Add "FLAKY_TEST" test directive to support re-running flaky tests.

Some of the mutex tests fail on machines with high load. This patch implements
the test directive "// FLAKY_TEST" which allows a test to be run 3 times
before it's considered a failure.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@280050 91177308-0d34-0410-b5e6-96231b3b80d8
16 files changed