clang-offload-bundler-zlib.c test behaves inconsistently in multistage ppc test bots

[eddyz87]

Hello,

While working on unrelated changes I noticed that test case ./clang/test/Driver/clang-offload-bundler-zlib.c (and ...-zstd.c variant) might randomly fail when run by ppc64le-lld-multistage-test builder. For example, here is a test run that fail after my commit, however the run immediately following it did not fail.

There are multiple instances of such behavior for ppc64le-lld-multistage-test and clang-ppc64le-linux-multistage builders:

• https://lab.llvm.org/buildbot/#/builders/36/builds/40413
• https://lab.llvm.org/buildbot/#/builders/36/builds/40425
• https://lab.llvm.org/buildbot/#/builders/121/builds/37027
• https://lab.llvm.org/buildbot/#/builders/121/builds/37033

Did not find examples for other builders, although the search was not exhaustive.
@gkistanova advised me to create this issue and assign it to test owner (@yxsamliu).

[yxsamliu]

Thanks for reporting the issue. I will fix it.