build: Announce environment variable usage to Cargo

This was primarily done to address issues from changing
LIBSSH_SYS_USE_PKG_CONFIG, but it's good build script practice to let
Cargo know of every used environment variable.

Closes: https://github.com/alexcrichton/ssh2-rs/issues/171

1 files changed, 3 insertions, 0 deletions

diff --git a/libssh2-sys/build.rs b/libssh2-sys/build.rs
index 861978d..57cf256 100644
--- a/libssh2-sys/build.rs
+++ b/libssh2-sys/build.rs
@@ -17,6 +17,7 @@ fn main() {
     // The system copy of libssh2 is not used by default because it
     // can lead to having two copies of libssl loaded at once.
     // See https://github.com/alexcrichton/ssh2-rs/pull/88
+    println!("cargo:rerun-if-env-changed=LIBSSH2_SYS_USE_PKG_CONFIG");
     if env::var("LIBSSH2_SYS_USE_PKG_CONFIG").is_ok() {
         if let Ok(lib) = pkg_config::find_library("libssh2") {
             for path in &lib.include_paths {
@@ -120,6 +121,7 @@ fn main() {
     cfg.define("LIBSSH2_DH_GEX_NEW", None);
 
     cfg.define("LIBSSH2_HAVE_ZLIB", None);
+    println!("cargo:rerun-if-env-changed=DEP_Z_INCLUDE");
     if let Some(path) = env::var_os("DEP_Z_INCLUDE") {
         cfg.include(path);
     } else if let Ok(lib) = pkg_config::find_library("zlib") {
@@ -128,6 +130,7 @@ fn main() {
         }
     }
 
+    println!("cargo:rerun-if-env-changed=DEP_OPENSSL_INCLUDE");
     if let Some(path) = env::var_os("DEP_OPENSSL_INCLUDE") {
         if let Some(path) = env::split_paths(&path).next() {
             if let Some(path) = path.to_str() {