Build SDL as universal binary

Xcode/SDL/SDL.xcodeproj/project.pbxproj

@@ -2788,6 +2788,7 @@
 		00CFA622106A567900758660 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				ARCHS = "$(ARCHS_STANDARD_32_64_BIT)";
 				CLANG_LINK_OBJC_RUNTIME = NO;
 				COMBINE_HIDPI_IMAGES = YES;
 				DYLIB_COMPATIBILITY_VERSION = 1.0.0;
@@ -2866,6 +2867,7 @@
 		00CFA628106A568900758660 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
+				ARCHS = "$(ARCHS_STANDARD_32_64_BIT)";
 				CLANG_LINK_OBJC_RUNTIME = NO;
 				COMBINE_HIDPI_IMAGES = YES;
 				DYLIB_COMPATIBILITY_VERSION = 1.0.0;