Define SDL_PLATFORM_* macros instead of underscored ones (#8875)

src/SDL_assert.c

@@ -20,20 +20,20 @@
 */
 #include "SDL_internal.h"
 
-#if defined(__WIN32__) || defined(__GDK__)
+#if defined(SDL_PLATFORM_WIN32) || defined(SDL_PLATFORM_GDK)
 #include "core/windows/SDL_windows.h"
 #endif
 
 #include "SDL_assert_c.h"
 #include "video/SDL_sysvideo.h"
 
-#if defined(__WIN32__) || defined(__GDK__)
+#if defined(SDL_PLATFORM_WIN32) || defined(SDL_PLATFORM_GDK)
 #ifndef WS_OVERLAPPEDWINDOW
 #define WS_OVERLAPPEDWINDOW 0
 #endif
 #endif
 
-#ifdef __EMSCRIPTEN__
+#ifdef SDL_PLATFORM_EMSCRIPTEN
     #include <emscripten.h>
     /* older Emscriptens don't have this, but we need to for wasm64 compatibility. */
     #ifndef MAIN_THREAD_EM_ASM_PTR
@@ -86,7 +86,7 @@ static void SDL_AddAssertionToReport(SDL_AssertData *data)
     }
 }
 
-#if defined(__WIN32__) || defined(__GDK__)
+#if defined(SDL_PLATFORM_WIN32) || defined(SDL_PLATFORM_GDK)
 #define ENDLINE "\r\n"
 #else
 #define ENDLINE "\n"
@@ -246,7 +246,7 @@ static SDL_AssertState SDLCALL SDL_PromptAssertion(const SDL_AssertData *data, v
             state = (SDL_AssertState)selected;
         }
     } else {
-#ifdef __EMSCRIPTEN__
+#ifdef SDL_PLATFORM_EMSCRIPTEN
         /* This is nasty, but we can't block on a custom UI. */
         for (;;) {
             SDL_bool okay = SDL_TRUE;