Use -static-libgcc only if the compiler is gcc

clang does not accept the -static-libgcc flag and apparently -static-libstdc++ is accepted but has no effect.

meson.build

@@ -28,7 +28,7 @@ foreach data_module : ['core', 'fonts', 'plugins', 'colors']
 endforeach
 
 lite_link_args = []
-if get_option('buildtype') == 'release'
+if cc.get_id() == 'gcc' and get_option('buildtype') == 'release'
   lite_link_args += ['-static-libgcc', '-static-libstdc++']
 endif