Use xcode clang on macos build

Author: RyeMutt

build/run.py

@@ -800,9 +800,11 @@ def build_webrtc(
                 'rtc_enable_symbol_export=true',
                 'rtc_enable_objc_symbol_export=false',
                 'use_custom_libcxx=false',
+                "use_custom_libcxx_for_host=false",
                 'treat_warnings_as_errors=false',
                 'clang_use_chrome_plugins=false',
                 'use_lld=false',
+                'is_clang=false',
             ]
         elif target in ('raspberry-pi-os_armv6',
                         'raspberry-pi-os_armv7',