Use SDL_PROCESS_WINDOWS instead of SDL_PLATFORM_WINDOWS

in SDL_process.c

[sdl-ci-filter cygwin]
[sdl-ci-filter msys2-*]
[sdl-ci-filter msvc-*]

Author: stahta01

src/process/SDL_process.c

@@ -45,7 +45,7 @@ SDL_Process *SDL_CreateProcess(const char * const *args, bool pipe_stdio)
 SDL_Process *SDL_CreateProcessWithProperties(SDL_PropertiesID props)
 {
     const char * const *args = SDL_GetPointerProperty(props, SDL_PROP_PROCESS_CREATE_ARGS_POINTER, NULL);
-#if defined(SDL_PLATFORM_WINDOWS)
+#if defined(SDL_PROCESS_WINDOWS)
     const char *cmdline = SDL_GetStringProperty(props, SDL_PROP_PROCESS_CREATE_CMDLINE_STRING, NULL);
     CHECK_PARAM((!args || !args[0] || !args[0][0]) && (!cmdline || !cmdline[0])) {
         SDL_SetError("Either SDL_PROP_PROCESS_CREATE_ARGS_POINTER or SDL_PROP_PROCESS_CREATE_CMDLINE_STRING must be valid");