Use SVN_REVISION, not SVN_VERSION.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97625 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/Version.cpp b/lib/Basic/Version.cpp
index 0c58b60..b9860cb 100644
--- a/lib/Basic/Version.cpp
+++ b/lib/Basic/Version.cpp
@@ -41,7 +41,7 @@
 
 std::string getClangRevision() {
 #ifdef SVN_REVISION
-  if (SVN_VERSION[0] != '\0') {
+  if (SVN_REVISION[0] != '\0') {
     std::string revision;
     llvm::raw_string_ostream OS(revision);
     OS << strtol(SVN_REVISION, 0, 10);