test: Add some common code to load test resources

As well as reducing duplication, this lets the tests load their resources
from the SDL_GetBasePath() on platforms that support it, which is useful
if the tests are compiled along with the rest of SDL and installed below
/usr as manual tests, similar to GNOME's installed-tests convention.

Thanks to Ozkan Sezer for the OS/2 build glue.

Co-authored-by: Ozkan Sezer <sezeroz@gmail.com>
Signed-off-by: Simon McVittie <smcv@collabora.com>

test/teststreaming.c

@@ -23,6 +23,7 @@
 #endif
 
 #include "SDL.h"
+#include "testutils.h"
 
 #define MOOSEPIC_W 64
 #define MOOSEPIC_H 88
@@ -128,6 +129,7 @@ main(int argc, char **argv)
 {
     SDL_Window *window;
     SDL_RWops *handle;
+    char *filename = NULL;
 
     /* Enable standard application logging */
     SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
@@ -138,7 +140,13 @@ main(int argc, char **argv)
     }
 
     /* load the moose images */
-    handle = SDL_RWFromFile("moose.dat", "rb");
+    filename = GetResourceFilename(NULL, "moose.dat");
+    if (filename == NULL) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Out of memory\n");
+        return -1;
+    }
+    handle = SDL_RWFromFile(filename, "rb");
+    SDL_free(filename);
     if (handle == NULL) {
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Can't find the file moose.dat !\n");
         quit(2);