Add 'REQUIRES: shell' to verbose-output-quoting.c

The lit shell couldn't handle these run lines.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@359081 91177308-0d34-0410-b5e6-96231b3b80d8

test/Driver/verbose-output-quoting.c

@@ -1,3 +1,4 @@
+// REQUIRES: shell
 // RUN: %clang --verbose -DSPACE="a b"  -c %s 2>&1 | FileCheck -check-prefix=SPACE     -strict-whitespace %s
 // RUN: %clang --verbose -DQUOTES=\"\"  -c %s 2>&1 | FileCheck -check-prefix=QUOTES    -strict-whitespace %s
 // RUN: %clang --verbose -DBACKSLASH=\\ -c %s 2>&1 | FileCheck -check-prefix=BACKSLASH -strict-whitespace %s