Revert "Meson: Avoid using add_global_arguments() when gst-build is a subproject" and fix it correctly.

This reverts commit ebcca1e5.

/utf-8 is needed to deal with subprojects that we do not control, so only set it when we're not a subproject. This is the correct fix for !236 (merged).

meson.build

@@ -59,6 +59,15 @@ if not meson.is_subproject() and cc.get_id() == 'msvc'
   endif
 endif
 
+# Ensure that MSVC interprets all source code as UTF-8. Only do this when we're
+# not a subproject, because subprojects are not allowed to call
+# add_global_arguments().
+if not meson.is_subproject() and cc.get_id() == 'msvc'
+  add_global_arguments(
+      cc.get_supported_arguments(['/utf-8']), # set the input encoding to utf-8
+      language: ['c', 'cpp'])
+endif
+
 # Ordered list of subprojects (dict has no ordering guarantees)
 subprojects = [
   ['gstreamer', {'build-hotdoc': true}],