Merge pull request #1723 from rasky/make_vars

Makefile: forward to xcode any variable declared on the command line
diff --git a/ExternalRevisions/SPIRV-Cross_repo_revision b/ExternalRevisions/SPIRV-Cross_repo_revision
index 2e77e6f..cc52676 100644
--- a/ExternalRevisions/SPIRV-Cross_repo_revision
+++ b/ExternalRevisions/SPIRV-Cross_repo_revision
@@ -1 +1 @@
-f6ca6178251c3c886d99781c5437df919fc21734
+81ba8f78f6646e5635129bd738f25bb3f43bbdb9