[SystemZ][z/OS]: fix lit tmp_dir to use - instead of _

[NancyWang2222]

Summary

Latest upstream change in https://reviews.llvm.org/D117179 causes lit regressions on z/OS, when TMPDIR is exported and contains _, ld linker fails, it doesnt recognize _ specified in SYSLIN. this seems a limitation on z/OS. we need to fix lit.

[yln]

Exact spelling of the temporary test directory shouldn't matter.
The z/OS linker not being able to handle this sounds like a bug... but oh my.

Nit: can we make the comment more compact, maybe:

tmp_dir = tempfile.mkdtemp(prefix='lit-tmp-')  # z/OS linker does not support '_' in paths, so use '-'

LGTM, thanks!

[mstorsjo]

Sounds reasonable to me - I don't think any other supported OSes would have an issue with that.

[NancyWang2222]

In D118071#3267521, @yln wrote:

Exact spelling of the temporary test directory shouldn't matter.
The z/OS linker not being able to handle this sounds like a bug... but oh my.

Nit: can we make the comment more compact, maybe:

tmp_dir = tempfile.mkdtemp(prefix='lit-tmp-')  # z/OS linker does not support '_' in paths, so use '-'

LGTM, thanks!

sure. I will update comments, I will put comment in separate line since it will be too long to fix in one line

[NancyWang2222]

Simplify the comments

[NancyWang2222]

In D118071#3267542, @mstorsjo wrote:

Sounds reasonable to me - I don't think any other supported OSes would have an issue with that.

Thanks.

llvm/utils/lit/lit/main.py

def execute_in_tmp_dir(run, lit_config):
     # Create a temp directory inside the normal temp directory so that we can
     # try to avoid temporary test file leaks. The user can avoid this behavior
     # by setting LIT_PRESERVES_TMP in the environment, so they can easily use
     # their own temp directory to monitor temporary file leaks or handle them at
     # the buildbot level.
     tmp_dir = None
     if 'LIT_PRESERVES_TMP' not in os.environ:
         import tempfile
-        tmp_dir = tempfile.mkdtemp(prefix='lit_tmp_')
+        # z/OS linker does not support '_' in paths, so use '-'.
+        tmp_dir = tempfile.mkdtemp(prefix='lit-tmp-')
         tmp_dir_envs = {k: tmp_dir for k in ['TMP', 'TMPDIR', 'TEMP', 'TEMPDIR']}
         os.environ.update(tmp_dir_envs)
         for cfg in {t.config for t in run.tests}:
             cfg.environment.update(tmp_dir_envs)
     try:
         run.execute()
     finally:
         if tmp_dir: