Fixed it

meson.build

@@ -2,7 +2,7 @@ project(
   'FluxEngine',
   'cpp',
   version : '0.1.0',
-  meson_version : '>=0.60.0',
+  meson_version : '>=0.63.0',
   default_options : [
     'cpp_std=c++20',
     'warning_level=3',
@@ -21,22 +21,10 @@ else
   dflag = '-D'
 endif
 
-# 3) Platform macro (all OSes)
-sys = host_machine.system()
-if sys == 'windows'
-  plat = 'FLUX_PLATFORM_WINDOWS'
-elif sys == 'linux'
-  plat = 'FLUX_PLATFORM_LINUX'
-elif sys == 'darwin'
-  plat = 'FLUX_PLATFORM_MACOS'
-elif sys == 'freebsd'
-  plat = 'FLUX_PLATFORM_FREEBSD'
-else
-  plat = 'FLUX_PLATFORM_UNKNOWN'
+if meson.get_compiler('cpp').get_id() == 'msvc'
+  add_project_arguments('/utf-8', language: 'cpp')
 endif
 
-add_global_arguments(dflag + plat, language : 'cpp')
-
 # 4) Build-type macros
 bt = get_option('buildtype')
 if bt == 'debug'