Add 'not' to commands that are expected to fail.

This is at least good documentation, but also opens the possibility of
using pipefail.

llvm-svn: 185652
diff --git a/clang/test/Index/pch-with-errors.c b/clang/test/Index/pch-with-errors.c
index 2d39613..5c94a8a 100644
--- a/clang/test/Index/pch-with-errors.c
+++ b/clang/test/Index/pch-with-errors.c
@@ -37,8 +37,8 @@
 // CHECK-INDEX: [indexDeclaration]: kind: function | name: foo
 // CHECK-INDEX: [indexEntityReference]: kind: function | name: erroneous
 
-// RUN: %clang -fsyntax-only %s -include %t.h 2>&1 | FileCheck -check-prefix=PCH-ERR %s
+// RUN: not %clang -fsyntax-only %s -include %t.h 2>&1 | FileCheck -check-prefix=PCH-ERR %s
 // PCH-ERR: error: PCH file contains compiler errors
 
-// RUN: c-index-test -write-pch %t.pch foobar.c 2>&1 | FileCheck -check-prefix=NONEXISTENT %s
+// RUN: not c-index-test -write-pch %t.pch foobar.c 2>&1 | FileCheck -check-prefix=NONEXISTENT %s
 // NONEXISTENT: Unable to load translation unit