CachePruning: fix typo, we accumulate file size here, not time

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266685 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/CachePruning.cpp

@@ -76,7 +76,7 @@ bool CachePruning::prune() {
           return;
         TotalSize += FileStatus.getSize();
         FileSizes.insert(
-            std::make_pair(FileAccessTime.seconds(), std::string(Path)));
+            std::make_pair(FileStatus.getSize(), std::string(Path)));
       };
 
   // Walk the entire directory cache, looking for unused files.