Conditionally compile MTLLanguageVersion2_3 based on available SDK.
diff --git a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
index 4add282..8735c1b 100644
--- a/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
+++ b/MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm
@@ -1218,7 +1218,8 @@
_metalFeatures.mslVersion = SPIRV_CROSS_NAMESPACE::CompilerMSL::Options::make_msl_version(maj, min);
switch (_metalFeatures.mslVersionEnum) {
-#if MVK_IOS_OR_TVOS
+#if (defined(__MAC_OS_X_VERSION_MAX_ALLOWED) && __MAC_OS_X_VERSION_MAX_ALLOWED >= 101600) || \
+ (defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 140000) // also covers tvOS
case MTLLanguageVersion2_3:
setMSLVersion(2, 3);
break;