Delete temporary output files when an error occurs during PCH reading.

This reduces the spam make test leaves behind in /tmp. The assert isn't
particularly useful because it's not run with -disable-free (the default when
using the clang driver) but should cover all -cc1 tests.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165910 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/FrontendAction.cpp b/lib/Frontend/FrontendAction.cpp
index ca85112..c8e41de 100644
--- a/lib/Frontend/FrontendAction.cpp
+++ b/lib/Frontend/FrontendAction.cpp
@@ -316,6 +316,7 @@
 
   if (HasBegunSourceFile)
     CI.getDiagnosticClient().EndSourceFile();
+  CI.clearOutputFiles(/*EraseFiles=*/true);
   setCurrentInput(FrontendInputFile());
   setCompilerInstance(0);
   return false;