guix: improve ENV unsetting for macOS

contrib/guix/libexec/build.sh

@@ -71,11 +71,9 @@ unset OBJCPLUS_INCLUDE_PATH
 
 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"
 
 case "$HOST" in
-    *darwin*) export LIBRARY_PATH="${NATIVE_GCC}/lib" ;;
+    *darwin*) export LIBRARY_PATH="${NATIVE_GCC}/lib" ;; # Required for qt/qmake
     *mingw*) export LIBRARY_PATH="${NATIVE_GCC}/lib" ;;
     *)
         NATIVE_GCC_STATIC="$(store_path gcc-toolchain static)"
@@ -180,6 +178,14 @@ make -C depends --jobs="$JOBS" HOST="$HOST" \
                                    x86_64_linux_NM=x86_64-linux-gnu-gcc-nm \
                                    x86_64_linux_STRIP=x86_64-linux-gnu-strip
 
+case "$HOST" in
+    *darwin*)
+        # Unset now that Qt is built
+        unset C_INCLUDE_PATH
+        unset CPLUS_INCLUDE_PATH
+        unset LIBRARY_PATH
+        ;;
+esac
 
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