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

test/testgeometry.c

@@ -12,17 +12,17 @@
 
 /* Simple program:  draw a RGB triangle, with texture  */
 
-#include <stdlib.h>
-#include <time.h>
-
-#ifdef __EMSCRIPTEN__
-#include <emscripten/emscripten.h>
-#endif
-
 #include <SDL3/SDL_test_common.h>
 #include <SDL3/SDL_main.h>
 #include "testutils.h"
 
+#ifdef SDL_PLATFORM_EMSCRIPTEN
+#include <emscripten/emscripten.h>
+#endif
+
+#include <stdlib.h>
+#include <time.h>
+
 static SDLTest_CommonState *state;
 static SDL_bool use_texture = SDL_FALSE;
 static SDL_Texture **sprites;
@@ -174,7 +174,7 @@ static void loop(void)
 
         SDL_RenderPresent(renderer);
     }
-#ifdef __EMSCRIPTEN__
+#ifdef SDL_PLATFORM_EMSCRIPTEN
     if (done) {
         emscripten_cancel_main_loop();
     }
@@ -266,7 +266,7 @@ int main(int argc, char *argv[])
     then = SDL_GetTicks();
     done = 0;
 
-#ifdef __EMSCRIPTEN__
+#ifdef SDL_PLATFORM_EMSCRIPTEN
     emscripten_set_main_loop(loop, 0, 1);
 #else
     while (!done) {