compilers: Check if GCC has support for ObjC and/or ObjC++

Since this is optional, we should not accept that GCC is a valid ObjC or
G++ is a valid ObjC++ Compiler unless we've tested that they can
actually do a basic compile.

mesonbuild/compilers/detect.py

@@ -877,9 +877,13 @@ def _detect_objc_or_objcpp_compiler(env: 'Environment', lang: str, for_machine:
             version = _get_gnu_version_from_defines(defines)
             comp = objc.GnuObjCCompiler if lang == 'objc' else objcpp.GnuObjCPPCompiler
             linker = guess_nix_linker(env, compiler, comp, version, for_machine)
-            return comp(
+            c = comp(
                 ccache, compiler, version, for_machine, is_cross, info,
                 defines, linker=linker)
+            if not c.compiles('int main(void) { return 0; }', env)[0]:
+                popen_exceptions[join_args(compiler)] = f'GCC was not built with support for {"objective-c" if lang == "objc" else "objective-c++"}'
+                continue
+            return c
         if 'clang' in out:
             linker = None
             defines = _get_clang_compiler_defines(compiler, lang)

unittests/machinefiletests.py

@@ -23,7 +23,7 @@
 import mesonbuild.environment
 import mesonbuild.coredata
 import mesonbuild.modules.gnome
-
+from mesonbuild import mesonlib
 from mesonbuild import machinefile
 
 from mesonbuild.mesonlib import (
@@ -275,7 +275,12 @@ def cb(comp):
             if not is_real_gnu_compiler(shutil.which('gcc')):
                 raise SkipTest('Only one compiler found, cannot test.')
             return 'gcc', 'gcc'
-        self.helper_for_compiler('objc', cb)
+        try:
+            self.helper_for_compiler('objc', cb)
+        except mesonlib.EnvironmentException as e:
+            if 'GCC was not built with support for objective-c' in str(e):
+                raise unittest.SkipTest("GCC doesn't support objective-c, test cannot run")
+            raise
 
     @skip_if_not_language('objcpp')
     @skip_if_env_set('OBJCXX')
@@ -288,7 +293,12 @@ def cb(comp):
             if not is_real_gnu_compiler(shutil.which('g++')):
                 raise SkipTest('Only one compiler found, cannot test.')
             return 'g++', 'gcc'
-        self.helper_for_compiler('objcpp', cb)
+        try:
+            self.helper_for_compiler('objcpp', cb)
+        except mesonlib.EnvironmentException as e:
+            if 'GCC was not built with support for objective-c++' in str(e):
+                raise unittest.SkipTest("G++ doesn't support objective-c++, test cannot run")
+            raise
 
     @skip_if_not_language('d')
     @skip_if_env_set('DC')