[-Wunsafe-buffer-usage] To disable a test on Windows systems.

One of the tests in the commit
'bdf4f2be' sometimes fails on one of
the buildbots runing on a Windows machine. For example,
"https://lab.llvm.org/buildbot/#/builders/60/builds/10615" is a failed
build.

Now we disable it until we figure out why this could happen.