Everywhere: Make Lagom build with GCC 13

GCC 13 was released on 2023-04-26. This commit fixes Lagom build errors
when using an updated host toolchain:
- Adds a workaround for a bug in constraint handling, which made LibJS
  fail to compile: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109683
- Silences the new `-Wdangling-reference` diagnostic globally. It
  produces multiple false positives with no clear way to silence them
  without `#pragmas`.
- Silences `-Wself-move` in `RefPtr` tests as GCC 13 adds this
  previously Clang-exclusive warning.

1 files changed, 3 insertions, 2 deletions

diff --git a/AK/Variant.h b/AK/Variant.h
index 46ed67c48b..372854f361 100644
--- a/AK/Variant.h
+++ b/AK/Variant.h
@@ -130,15 +130,16 @@ struct VariantConstructTag {
 
 template<typename T, typename Base>
 struct VariantConstructors {
+    // The pointless `typename Base` constraints are a workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109683
     ALWAYS_INLINE VariantConstructors(T&& t)
-    requires(requires { T(move(t)); })
+    requires(requires { T(move(t)); typename Base; })
     {
         internal_cast().clear_without_destruction();
         internal_cast().set(move(t), VariantNoClearTag {});
     }
 
     ALWAYS_INLINE VariantConstructors(T const& t)
-    requires(requires { T(t); })
+    requires(requires { T(t); typename Base; })
     {
         internal_cast().clear_without_destruction();
         internal_cast().set(t, VariantNoClearTag {});