build: Use cc.get_supported_arguments() instead of open-coding

I added support to Meson for cc.get_supported_arguments() when I was
typing out the initial build because I didn't like the open-coding, then
completely forgot to update Weston when it got merged.

Signed-off-by: Daniel Stone <daniels@collabora.com>

meson.build

@@ -60,8 +60,7 @@ config_h = configuration_data()
 
 cc = meson.get_compiler('c')
 
-global_args = []
-global_args_maybe = [
+global_args = cc.get_supported_arguments(
 	'-Wmissing-prototypes',
 	'-Wno-unused-parameter',
 	'-Wno-shift-negative-value', # required due to Pixman
@@ -69,12 +68,7 @@ global_args_maybe = [
 	'-Wno-pedantic',
 	'-Wundef',
 	'-fvisibility=hidden',
-]
-foreach a : global_args_maybe
-	if cc.has_argument(a)
-		global_args += a
-	endif
-endforeach
+)
 add_global_arguments(global_args, language: 'c')
 
 if cc.has_header_symbol('sys/sysmacros.h', 'major')