[llvm-config] Fix cflags test looking for "error"

This test is (I think) actually trying to make sure no errors are printed, but it hits on the string "error" in flags.

llvm-svn: 289484

llvm/test/tools/llvm-config/cflags.test

@@ -3,5 +3,5 @@ RUN: llvm-config --cppflags 2>&1 | FileCheck %s
 RUN: llvm-config --cxxflags 2>&1 | FileCheck %s
 CHECK: -I
 CHECK: {{[/\\]}}include
-CHECK-NOT: error
+CHECK-NOT: error:
 CHECK-NOT: warning