meson: error on MSVCRT builds

MSVCRT requires wide string APIs, which were removed. Instead of dealing
with this, just error out on it. MSVCRT is deprecated anyway.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

meson.build

@@ -17,12 +17,10 @@ else
 endif
 
 if host_machine.system() == 'windows'
-  if cpp.get_argument_syntax() == 'gcc'
-    if cpp.compiles('#include <time.h>\n#ifdef _UCRT\n#error\n#endif')
-      add_project_arguments('-D__USE_MINGW_ANSI_STDIO', '-D__MINGW_USE_VC2005_COMPAT', language: 'cpp')
-    endif
-  else
+  if cpp.get_argument_syntax() == 'msvc'
     add_project_arguments('-DNOMINMAX', language: 'cpp')
+  elif cpp.compiles('#include <time.h>\n#ifdef _UCRT\n#error\n#endif')
+    error('Non UCRT MinGW is unsupported. Please update toolchain')
   endif
 endif