Hiding OpenGLES API deprecation since iOS 12.0 warning

Xcode/SDL/SDL.xcodeproj/project.pbxproj

@@ -3240,6 +3240,7 @@
 			baseConfigurationReference = F3F7BE3B2CBD79D200C984AF /* config.xcconfig */;
 			buildSettings = {
 				CLANG_LINK_OBJC_RUNTIME = NO;
+				GCC_PREPROCESSOR_DEFINITIONS = GLES_SILENCE_DEPRECATION;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				GCC_GENERATE_DEBUGGING_SYMBOLS = YES;
 				OTHER_LDFLAGS = "-liconv";
@@ -3304,6 +3305,7 @@
 			baseConfigurationReference = F3F7BE3B2CBD79D200C984AF /* config.xcconfig */;
 			buildSettings = {
 				CLANG_LINK_OBJC_RUNTIME = NO;
+				GCC_PREPROCESSOR_DEFINITIONS = GLES_SILENCE_DEPRECATION;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				GCC_GENERATE_DEBUGGING_SYMBOLS = YES;
 				OTHER_LDFLAGS = "-liconv";