guix: More thoroughly control native toolchain

contrib/guix/libexec/build.sh

@@ -54,16 +54,34 @@ store_path() {
 # Set environment variables to point the NATIVE toolchain to the right
 # includes/libs
 NATIVE_GCC="$(store_path gcc-toolchain)"
-export LIBRARY_PATH="${NATIVE_GCC}/lib:${NATIVE_GCC}/lib64"
-export CPATH="${NATIVE_GCC}/include"
+
+unset LIBRARY_PATH
+unset CPATH
 unset C_INCLUDE_PATH
 unset CPLUS_INCLUDE_PATH
+unset OBJC_INCLUDE_PATH
+unset OBJCPLUS_INCLUDE_PATH
+
+export LIBRARY_PATH="${NATIVE_GCC}/lib:${NATIVE_GCC}/lib64"
+export C_INCLUDE_PATH="${NATIVE_GCC}/include"
+export CPLUS_INCLUDE_PATH="${NATIVE_GCC}/include/c++:${NATIVE_GCC}/include"
+export OBJC_INCLUDE_PATH="${NATIVE_GCC}/include"
+export OBJCPLUS_INCLUDE_PATH="${NATIVE_GCC}/include/c++:${NATIVE_GCC}/include"
+
+prepend_to_search_env_var() {
+    export "${1}=${2}${!1:+:}${!1}"
+}
+
 case "$HOST" in
     *darwin*)
         # When targeting darwin, zlib is required by native_libdmg-hfsplus.
         zlib_store_path=$(store_path "zlib")
-        export LIBRARY_PATH="${zlib_store_path}/lib:${LIBRARY_PATH}"
-        export CPATH="${zlib_store_path}/include:${CPATH}"
+
+        prepend_to_search_env_var LIBRARY_PATH "${zlib_store_path}/lib"
+        prepend_to_search_env_var C_INCLUDE_PATH "${zlib_store_path}/include"
+        prepend_to_search_env_var CPLUS_INCLUDE_PATH "${zlib_store_path}/include"
+        prepend_to_search_env_var OBJC_INCLUDE_PATH "${zlib_store_path}/include"
+        prepend_to_search_env_var OBJCPLUS_INCLUDE_PATH "${zlib_store_path}/include"
 esac
 
 # Set environment variables to point the CROSS toolchain to the right

depends/packages/qt.mk

@@ -10,7 +10,7 @@ $(package)_patches=fix_qt_pkgconfig.patch mac-qmake.conf fix_no_printer.patch no
 $(package)_patches+= fix_android_qmake_conf.patch fix_android_jni_static.patch dont_hardcode_pwd.patch
 $(package)_patches+= drop_lrelease_dependency.patch no_sdk_version_check.patch
 $(package)_patches+= fix_qpainter_non_determinism.patch fix_lib_paths.patch fix_android_pch.patch
-$(package)_patches+= fix_bigsur_drawing.patch
+$(package)_patches+= fix_bigsur_drawing.patch qtbase-moc-ignore-gcc-macro.patch
 
 $(package)_qttranslations_file_name=qttranslations-$($(package)_suffix)
 $(package)_qttranslations_sha256_hash=e1de58ed108b7e0a138815ea60fd46a2c4e1fc31396a707e5630e92de79c53de
@@ -232,6 +232,7 @@ define $(package)_preprocess_cmds
   patch -p1 -i $($(package)_patch_dir)/no_sdk_version_check.patch && \
   patch -p1 -i $($(package)_patch_dir)/fix_lib_paths.patch && \
   patch -p1 -i $($(package)_patch_dir)/fix_bigsur_drawing.patch && \
+  patch -p1 -i $($(package)_patch_dir)/qtbase-moc-ignore-gcc-macro.patch && \
   sed -i.old "s|updateqm.commands = \$$$$\$$$$LRELEASE|updateqm.commands = $($(package)_extract_dir)/qttools/bin/lrelease|" qttranslations/translations/translations.pro && \
   mkdir -p qtbase/mkspecs/macx-clang-linux &&\
   cp -f qtbase/mkspecs/macx-clang/qplatformdefs.h qtbase/mkspecs/macx-clang-linux/ &&\

depends/patches/qt/qtbase-moc-ignore-gcc-macro.patch

@@ -0,0 +1,17 @@
+The moc executable loops through headers on CPLUS_INCLUDE_PATH and stumbles
+on the GCC internal _GLIBCXX_VISIBILITY macro.  Tell it to ignore it as it is
+not supposed to be looking there to begin with.
+
+Upstream report: https://bugreports.qt.io/browse/QTBUG-83160
+
+diff --git a/qtbase/src/tools/moc/main.cpp b/qtbase/src/tools/moc/main.cpp
+--- a/qtbase/src/tools/moc/main.cpp
++++ b/qtbase/src/tools/moc/main.cpp
+@@ -188,6 +188,7 @@ int runMoc(int argc, char **argv)
+     dummyVariadicFunctionMacro.arguments += Symbol(0, PP_IDENTIFIER, "__VA_ARGS__");
+     pp.macros["__attribute__"] = dummyVariadicFunctionMacro;
+     pp.macros["__declspec"] = dummyVariadicFunctionMacro;
++    pp.macros["_GLIBCXX_VISIBILITY"] = dummyVariadicFunctionMacro;
+
+     QString filename;
+     QString output;