Make file_status::getUniqueID const.

llvm-svn: 187383
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 0c4518c..4dcfa09 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -293,7 +293,7 @@
   return Ret;
 }
 
-UniqueID file_status::getUniqueID() {
+UniqueID file_status::getUniqueID() const {
   return UniqueID(fs_st_dev, fs_st_ino);
 }