[gtk/gtk3.meson.msvc.improvements] meson/MSVC builds: Use -utf-8 where available

[Chun-wei Fan <fanchunwei src gnome org>]

commit c0d5f556851908caba1402fe53504101af80e127
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Wed Jan 15 15:27:59 2020 +0800

    meson/MSVC builds: Use -utf-8 where available
    
    This avoids the build from erroring out on C4819 (Unicode handling issue in
    Visual Studio compiler), notably when running on CHinese, Japanese and
    Korean locales.

 meson.build | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/meson.build b/meson.build
index 6d6f919fd8..d6162b428e 100644
--- a/meson.build
+++ b/meson.build
@@ -274,9 +274,12 @@ endif
 if cc.get_id() == 'msvc'
   # Compiler options taken from msvc_recommended_pragmas.h
   # in GLib, based on _Win32_Programming_ by Rector and Newcomer
-  test_cflags = []
-  add_project_arguments('-FImsvc_recommended_pragmas.h', language: 'c')
-  add_project_arguments('-D_USE_MATH_DEFINES', language: 'c')
+  test_cflags = [
+    '-FImsvc_recommended_pragmas.h',
+       '-D_USE_MATH_DEFINES',
+       '-utf-8',
+  ]
+  add_project_arguments(cc.get_supported_arguments(test_cflags), language: 'c')
 elif cc.get_id() == 'gcc' or cc.get_id() == 'clang'
   test_cflags = [
     '-fno-strict-aliasing',