ui/sdl2: Check return value from g_setenv()

Setting environment variables can fail; check the return value
from g_setenv() and bail out if we couldn't set SDL_VIDEODRIVER.

Fixes: Coverity 1458798
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20210809161424.32355-1-peter.maydell@linaro.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/sdl2.c

@@ -817,7 +817,10 @@ static void sdl2_display_init(DisplayState *ds, DisplayOptions *o)
      * This is a bit hackish but saves us from bigger problem.
      * Maybe it's a good idea to fix this in SDL instead.
      */
-    g_setenv("SDL_VIDEODRIVER", "x11", 0);
+    if (!g_setenv("SDL_VIDEODRIVER", "x11", 0)) {
+        fprintf(stderr, "Could not set SDL_VIDEODRIVER environment variable\n");
+        exit(1);
+    }
 #endif
 
     if (SDL_Init(SDL_INIT_VIDEO)) {