Meta: Switch to a SuperBuild that splits host and target builds

Replace the old logic where we would start with a host build, and swap
all the CMake compiler and target variables underneath it to trick
CMake into building for Serenity after we configured and built the Lagom
code generators.

The SuperBuild creates two ExternalProjects, one for Lagom and one for
Serenity. The Serenity project depends on the install stage for the
Lagom build. The SuperBuild also generates a CMakeToolchain file for the
Serenity build to use that replaces the old toolchain file that was only
used for Ports.

To ensure that code generators are rebuilt when core libraries such as
AK and LibCore are modified, developers will need to direct their manual
`ninja` invocations to the SuperBuild's binary directory instead of the
Serenity binary directory.

This commit includes warning coalescing and option style cleanup for the
affected CMakeLists in the Kernel, top level, and runtime support
libraries. A large part of the cleanup is replacing USE_CLANG_TOOLCHAIN
with the proper CMAKE_CXX_COMPILER_ID variable, which will no longer be
confused by a host clang compiler.

1 files changed, 67 insertions, 79 deletions

diff --git a/Meta/Lagom/CMakeLists.txt b/Meta/Lagom/CMakeLists.txt
index 69fcdd6a5c..e9f02ac40c 100644
--- a/Meta/Lagom/CMakeLists.txt
+++ b/Meta/Lagom/CMakeLists.txt
@@ -8,9 +8,10 @@ project(
     LANGUAGES C CXX
 )
 
-option(BUILD_SHARED_LIBS "Build shared libraries instead of static libraries" ON)
-if (ENABLE_OSS_FUZZ)
-    set(BUILD_SHARED_LIBS OFF) # Don't use shared libraries on oss-fuzz, for ease of integration with their infrastructure
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "10.2")
+  message(FATAL_ERROR
+      "A GCC version less than 10.2 was detected (${CMAKE_CXX_COMPILER_VERSION}), this is unsupported.\n"
+      "Please re-read the build instructions documentation, and upgrade your host compiler.\n")
 endif()
 
 # This is required for CMake (when invoked for a Lagom-only build) to
@@ -33,12 +34,22 @@ endif()
 
 include(lagom_options)
 
+if(ENABLE_ALL_THE_DEBUG_MACROS)
+    include(all_the_debug_macros)
+endif()
+
+option(BUILD_SHARED_LIBS "Build shared libraries instead of static libraries" ON)
+if (ENABLE_OSS_FUZZ)
+    set(BUILD_SHARED_LIBS OFF) # Don't use shared libraries on oss-fuzz, for ease of integration with their infrastructure
+endif()
+
 find_package(Threads REQUIRED)
 
 if (ENABLE_LAGOM_CCACHE)
     find_program(CCACHE_PROGRAM ccache)
     if(CCACHE_PROGRAM)
-        set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_PROGRAM}")
+        set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_PROGRAM}" CACHE FILEPATH "Path to a compiler launcher program, e.g. ccache")
+        set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_PROGRAM}" CACHE FILEPATH "Path to a compiler launcher program, e.g. ccache")
     endif()
 endif()
 
@@ -58,7 +69,7 @@ set(CMAKE_BUILD_WITH_INSTALL_RPATH FALSE)
 # See slide 100 of the following ppt :^)
 # https://crascit.com/wp-content/uploads/2019/09/Deep-CMake-For-Library-Authors-Craig-Scott-CppCon-2019.pdf
 if (NOT APPLE)
-    set(CMAKE_INSTALL_RPATH $ORIGIN)
+    set(CMAKE_INSTALL_RPATH $ORIGIN:$ORIGIN/../lib)
 endif()
 set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
 
@@ -79,7 +90,7 @@ if (ENABLE_UNDEFINED_SANITIZER)
     set(LINKER_FLAGS "${LINKER_FLAGS} -fsanitize=undefined -fno-sanitize=vptr")
 endif()
 
-if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang$")
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang$")
     # Clang's default constexpr-steps limit is 1048576(2^20), GCC doesn't have one
     add_compile_options(-Wno-overloaded-virtual -Wno-user-defined-literals -fconstexpr-steps=16777216)
 
@@ -88,7 +99,7 @@ if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang$")
         set(LINKER_FLAGS "${LINKER_FLAGS} -fsanitize=fuzzer")
     endif()
 
-elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     add_compile_options(-Wno-expansion-to-defined)
 endif()
 
@@ -101,11 +112,7 @@ set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${LINKER_FLAGS}")
 set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${LINKER_FLAGS}")
 set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} ${LINKER_FLAGS}")
 
-# FIXME: This is a hack, because the lagom stuff can be built individually or
-#        in combination with the system, we generate two Debug.h files. One in
-#        Build/AK/Debug.h and the other in Build/Meta/Lagom/AK/Debug.h.
 configure_file(../../AK/Debug.h.in AK/Debug.h @ONLY)
-configure_file(../../Kernel/Debug.h.in Kernel/Debug.h @ONLY)
 
 include_directories(../../)
 include_directories(../../Userland/)
@@ -114,59 +121,36 @@ include_directories(${CMAKE_BINARY_DIR})
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 
 # install rules, think about moving to its own helper cmake file
-# Don't install Lagom libs into the target Root/
-# FIXME: Remove this check for 4594
-if (CMAKE_SOURCE_DIR MATCHES ".*/Lagom")
-    include(CMakePackageConfigHelpers)
-    include(GNUInstallDirs)
-
-    # find_package(<package>) call for consumers to find this project
-    set(package Lagom)
-
-    write_basic_package_version_file(
-        "${package}ConfigVersion.cmake"
-        COMPATIBILITY SameMajorVersion
-    )
-
-    # Allow package maintainers to freely override the path for the configs
-    set(Lagom_INSTALL_CMAKEDIR "${CMAKE_INSTALL_DATADIR}/${package}"
-        CACHE PATH "CMake package config location relative to the install prefix")
-    mark_as_advanced(Lagom_INSTALL_CMAKEDIR)
-
-    install(
-        FILES ${SERENITY_PROJECT_ROOT}/Meta/CMake/lagom-install-config.cmake
-        DESTINATION "${Lagom_INSTALL_CMAKEDIR}"
-        RENAME "${package}Config.cmake"
-        COMPONENT Lagom_Development
-    )
-
-    install(
-        FILES "${PROJECT_BINARY_DIR}/${package}ConfigVersion.cmake"
-        DESTINATION "${Lagom_INSTALL_CMAKEDIR}"
-        COMPONENT Lagom_Development
-    )
-
-    install(
-        EXPORT LagomTargets
-        NAMESPACE Lagom::
-        DESTINATION "${Lagom_INSTALL_CMAKEDIR}"
-        COMPONENT Lagom_Development
-    )
+include(CMakePackageConfigHelpers)
+include(GNUInstallDirs)
+
+# find_package(<package>) call for consumers to find this project
+set(package Lagom)
+
+# Allow package maintainers to freely override the path for the configs
+set(Lagom_INSTALL_CMAKEDIR "${CMAKE_INSTALL_DATADIR}/${package}"
+    CACHE PATH "CMake package config location relative to the install prefix")
+mark_as_advanced(Lagom_INSTALL_CMAKEDIR)
+
+install(
+    FILES "${SERENITY_PROJECT_ROOT}/Meta/CMake/lagom-install-config.cmake"
+    DESTINATION "${Lagom_INSTALL_CMAKEDIR}"
+    RENAME "${package}Config.cmake"
+    COMPONENT Lagom_Development
+)
 
-    # Manually install AK
-    install(
-        DIRECTORY "${SERENITY_PROJECT_ROOT}/AK"
-        COMPONENT Lagom_Development
-        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-        FILES_MATCHING PATTERN "*.h"
-    )
-endif()
+install(
+    EXPORT LagomTargets
+    NAMESPACE Lagom::
+    DESTINATION "${Lagom_INSTALL_CMAKEDIR}"
+    COMPONENT Lagom_Development
+)
 
 function(lagom_lib library fs_name)
     cmake_parse_arguments(LAGOM_LIBRARY "" "" "SOURCES;LIBS" ${ARGN})
     set(target_name "Lagom${library}")
     add_library(${target_name} ${LAGOM_LIBRARY_SOURCES})
-    # alias for pretty exports
+    # alias for parity with exports
     add_library(Lagom::${library} ALIAS ${target_name})
 
     set_target_properties(
@@ -180,29 +164,25 @@ function(lagom_lib library fs_name)
     if (NOT ${target_name} STREQUAL "LagomCore")
         target_link_libraries(${target_name} LagomCore)
     endif()
-    # Don't install Lagom libs into the target Root/
-    # FIXME: Remove this check for 4594
-    if (CMAKE_SOURCE_DIR MATCHES ".*/Lagom")
-        install(
-            TARGETS ${target_name}
-            EXPORT LagomTargets
-            RUNTIME #
-                COMPONENT Lagom_Runtime
-            LIBRARY #
-                COMPONENT Lagom_Runtime
-                NAMELINK_COMPONENT Lagom_Development
-            ARCHIVE #
-                COMPONENT Lagom_Development
-            INCLUDES #
-                DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-        )
-        install(
-            DIRECTORY "${SERENITY_PROJECT_ROOT}/Userland/Libraries/Lib${library}"
+    install(
+        TARGETS ${target_name}
+        EXPORT LagomTargets
+        RUNTIME #
+            COMPONENT Lagom_Runtime
+        LIBRARY #
+            COMPONENT Lagom_Runtime
+            NAMELINK_COMPONENT Lagom_Development
+        ARCHIVE #
             COMPONENT Lagom_Development
+        INCLUDES #
             DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-            FILES_MATCHING PATTERN "*.h"
-        )
-    endif()
+    )
+    install(
+        DIRECTORY "${SERENITY_PROJECT_ROOT}/Userland/Libraries/Lib${library}"
+        COMPONENT Lagom_Development
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+        FILES_MATCHING PATTERN "*.h"
+    )
 endfunction()
 
 function(lagom_test source)
@@ -229,6 +209,14 @@ if (NOT APPLE)
     target_link_libraries(LagomCore crypt) # Core::Account uses crypt() but it's not in libcrypt on macOS
 endif()
 
+# Manually install AK headers
+install(
+    DIRECTORY "${SERENITY_PROJECT_ROOT}/AK"
+    COMPONENT Lagom_Development
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    FILES_MATCHING PATTERN "*.h"
+)
+
 # Code Generators and other host tools
 # We need to make sure not to build code generators for Fuzzer builds, as they already have their own main.cpp
 if (NOT ENABLE_OSS_FUZZ AND NOT ENABLE_FUZZER_SANITIZER)