Use -NOT prefix instead of adding not to FileCheck.

If we want to make sure that a particular string is not in an output,
the regular way of doing it is to add `-NOT` prefix instead of checking
if FileCheck resulted in an error.

Differential Revision: https://reviews.llvm.org/D34435

llvm-svn: 305930

clang/test/Driver/autocomplete.c

@@ -2,8 +2,8 @@
 // FSYN: -fsyntax-only
 // RUN: %clang --autocomplete=-s | FileCheck %s -check-prefix=STD
 // STD: -std={{.*}}-stdlib=
-// RUN: %clang --autocomplete=foo | not FileCheck %s -check-prefix=NONE
-// NONE: foo
+// RUN: %clang --autocomplete=foo | FileCheck %s -check-prefix=FOO
+// FOO-NOT: foo
 // RUN: %clang --autocomplete=-stdlib=,l | FileCheck %s -check-prefix=STDLIB
 // STDLIB: libc++ libstdc++
 // RUN: %clang --autocomplete=-stdlib=, | FileCheck %s -check-prefix=STDLIBALL