Disable MTLLanguageVersion2_3 on macOS for Xcode 12.0.
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
index 614f064..4add282 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
@@ -1218,9 +1218,11 @@
_metalFeatures.mslVersion = SPIRV_CROSS_NAMESPACE::CompilerMSL::Options::make_msl_version(maj, min);
switch (_metalFeatures.mslVersionEnum) {
+#if MVK_IOS_OR_TVOS
case MTLLanguageVersion2_3:
setMSLVersion(2, 3);
break;
+#endif
case MTLLanguageVersion2_2:
setMSLVersion(2, 2);
break;