[clang/test] Fix a flaky unittest on windows
Summary:
The append operator on a shell command for quick command-line is
causing trouble on windows. [NFC]
The easiest way to fix them is to avoid using them.
This patch is an attempt to fix this broken build bot:
clang-x86-win2008-selfhost
http://lab.llvm.org:8011/builders/clang-x86-win2008-selfhost/builds/9523
Reviewers: rnk
Subscribers: cfe-commits, chrisha
Differential Revision: https://reviews.llvm.org/D23105
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@277576
91177308-0d34-0410-b5e6-
96231b3b80d8