[llvm-ar][test][AIX] Unsupport error-opening-directory.test on AIX

[stevewan]

Summary

The test fails on AIX as it allows open() and read() on a directory. This patch adds `# UNSUPPORTED:
system-aix` to the test to prevent it from running on AIX.

[stevewan]

FYI @sameerarora101, we on AIX are experiencing the exact same failure as what has been fixed in D82786 for FreeBSD. This patch adds AIX to the unsupported list as well.

[hubert.reinterpretcast]

LGTM. Please give other reviewers some time to comment; thanks.

[MaskRay]

Thanks!

[sameerarora101]

@stevewan Thanks for reporting and the fix. Sorry about the breakage!

[smeenai]

Thanks and sorry for the breakage!

[ShuhongL]

LGTM.

[MaskRay]

@stevenwan

Hi, your git commit contains extra Phabricator tags. You can drop Reviewers: Subscribers: Tags: and the text Summary: from the git commit with the following script:

arcfilter () {
        arc amend
        git log -1 --pretty=%B | awk '/Reviewers:|Subscribers:/{p=1} /Reviewed By:|Differential Revision:/{p=0} !p && !/^Summary:$/ {sub(/^Summary: /,"");print}' | git commit --amend --date=now -F -
}

Reviewed By: is considered important by some people. Please keep the tag. (--date=now is my personal preference (author dates are usually not useful. Using committer dates can make log almost monotonic in time))

llvm/utils/git/pre-push.py can validate the message does not include unneeded tags. Please clean up tags for future commits. Thanks.

llvm/test/tools/llvm-ar/error-opening-directory.test

-## Unsupported on FreeBSD as FreeBSD 12 and earlier allow reading directories
-## by default.
-# UNSUPPORTED: system-freebsd
+## Unsupported on AIX and FreeBSD as AIX and FreeBSD 12 and earlier allow
+## reading directories by default.
+# UNSUPPORTED: system-freebsd, system-aix
 
 # RUN: rm -rf %t && mkdir -p %t
 
 ## Passing in a directory:
 # RUN: mkdir -p %t/tmpDir
 # RUN: not llvm-ar p %t/tmpDir 2>&1 | \
 # RUN:    FileCheck %s --check-prefix=IS-DIR -DARCHIVE=%t/tmpDir
 
 # IS-DIR: error: unable to open '[[ARCHIVE]]': {{[iI]}}s a directory