build-moltenvk: enable MVK_USE_METAL_PRIVATE_API

Author: m154k1

build-moltenvk

@@ -20,7 +20,7 @@ cd "${srcdir}"
 sed -i '' 's/xcodebuild "$@"/'"${xcodebuild}"' "$@"/g' fetchDependencies
 sed -Ei '' 's/(XCODEBUILD := ).*/\1'"${xcodebuild}"'/' Makefile
 ./fetchDependencies --macos --v-headers-root "${PREFIX}"
-make macos MVK_CONFIG_LOG_LEVEL=1 "$@"
+make macos MVK_CONFIG_LOG_LEVEL=1 MVK_USE_METAL_PRIVATE_API=1 "$@"
 
 sed -i '' 's;\./;../../../lib/;' "${builddir}"/MoltenVK_icd.json
 echo