[lit] Remove stale test inputs before running check-lit

This should fix googletest-format test failures on the clang modules
buildbots, which have a stale copy of the OneTest script in the build
directory.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@309432 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed