- fixed ARM64 compilation issues reported by Xcode 12 beta 4

src/common/engine/stats.h:139:31: error: invalid output constraint '=A' in asm
src/common/platform/posix/osx/iwadpicker_cocoa.mm:379:1: warning: non-void function does not return a value [-Wreturn-type]

src/common/engine/stats.h

@@ -132,6 +132,9 @@ inline uint64_t rdtsc()
 	}
 	while (upper != temp);
 	return (static_cast<unsigned long long>(upper) << 32) | lower;
+#elif defined __aarch64__
+	// TODO: Implement and test on ARM64
+	return 0;
 #else // i386
 	if (CPU.bRDTSC)
 	{

src/common/platform/posix/osx/iwadpicker_cocoa.mm

@@ -375,6 +375,8 @@ static NSString* GetArchitectureString()
 	return @"i386";
 #elif defined __x86_64__
 	return @"x86_64";
+#elif defined __aarch64__
+	return @"arm64";
 #endif
 }