iOS/tvOS: minor xcode cleanup (libretro#15957)

This hopefully makes debug and release easier to manage by making
their C flags the same and moving the differences to the preprocessor
macros.

pkg/apple/RetroArch_iOS13.xcodeproj/project.pbxproj

@@ -2141,6 +2141,10 @@
 				ENABLE_BITCODE = NO;
 				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_OPTIMIZATION_LEVEL = 2;
+				GCC_PREPROCESSOR_DEFINITIONS = (
+					NDEBUG,
+					"NS_BLOCK_ASSERTIONS=1",
+				);
 				GCC_WARN_ABOUT_RETURN_TYPE = YES;
 				GCC_WARN_UNINITIALIZED_AUTOS = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
@@ -2229,8 +2233,6 @@
 					"-DHAVE_ZLIB",
 					"-DINLINE=inline",
 					"-DIOS",
-					"-DNDEBUG",
-					"-DNS_BLOCK_ASSERTIONS=1",
 					"-DRARCH_INTERNAL",
 					"-DRARCH_MOBILE",
 					"-DRC_DISABLE_LUA",