depends: Specify Objective C/C++ compilers for native_qt package

This change fixes cross-compilation from macOS to macOS with another
architecture.

Author: hebasto

depends/packages/native_qt.mk

@@ -88,6 +88,10 @@ $(package)_config_opts += -no-feature-qtplugininfo
 
 $(package)_config_env := CC="$$(build_CC)"
 $(package)_config_env += CXX="$$(build_CXX)"
+ifeq ($(build_os),darwin)
+$(package)_config_env += OBJC="$$(build_CC)"
+$(package)_config_env += OBJCXX="$$(build_CXX)"
+endif
 
 $(package)_cmake_opts := -DCMAKE_EXE_LINKER_FLAGS="$$(build_LDFLAGS)"
 ifneq ($(V),)