Worked around "Undefined symbol: ___isPlatformVersionAtLeast()" link error on Xcode 11 beta

src/render/metal/SDL_render_metal.m

@@ -1733,11 +1733,12 @@ METAL_CreateRenderer(SDL_Window * window, Uint32 flags)
 #endif
 #else
 #ifdef __IPHONE_11_0
-    if (@available(iOS 11.0, *)) {
-        if ([mtldevice supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily4_v1]) {
-            maxtexsize = 16384;
-        }
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
+    if ([mtldevice supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily4_v1]) {
+        maxtexsize = 16384;
     } else
+#pragma clang diagnostic pop
 #endif
 #ifdef __IPHONE_10_0
     if ([mtldevice supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily3_v1]) {

src/video/uikit/SDL_uikitvideo.m

@@ -230,10 +230,13 @@ UIKit_ForceUpdateHomeIndicator()
     if (focus) {
         SDL_WindowData *data = (__bridge SDL_WindowData *) focus->driverdata;
         if (data != nil) {
-            if (@available(iOS 11.0, *)) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
+            if ([data.viewcontroller respondsToSelector:@selector(setNeedsUpdateOfHomeIndicatorAutoHidden)]) {
                 [data.viewcontroller performSelectorOnMainThread:@selector(setNeedsUpdateOfHomeIndicatorAutoHidden) withObject:nil waitUntilDone:NO];
                 [data.viewcontroller performSelectorOnMainThread:@selector(setNeedsUpdateOfScreenEdgesDeferringSystemGestures) withObject:nil waitUntilDone:NO];
             }
+#pragma clang diagnostic pop
         }
     }
 #endif /* !TARGET_OS_TV */

src/video/uikit/SDL_uikitviewcontroller.m

@@ -57,10 +57,13 @@ SDL_HideHomeIndicatorHintChanged(void *userdata, const char *name, const char *o
     @autoreleasepool {
         SDL_uikitviewcontroller *viewcontroller = (__bridge SDL_uikitviewcontroller *) userdata;
         viewcontroller.homeIndicatorHidden = (hint && *hint) ? SDL_atoi(hint) : -1;
-        if (@available(iOS 11.0, *)) {
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability-new"
+        if ([viewcontroller respondsToSelector:@selector(setNeedsUpdateOfHomeIndicatorAutoHidden)]) {
             [viewcontroller setNeedsUpdateOfHomeIndicatorAutoHidden];
             [viewcontroller setNeedsUpdateOfScreenEdgesDeferringSystemGestures];
         }
+#pragma clang diagnostic pop
     }
 }
 #endif