[lld] [test] Fix reproduce-blackslash.s test with NetBSD tar

[mgorny]

Summary

Unlike GNU tar and libarchive bsdtar, NetBSD 'tar -t' output does not
use C-style escapes and instead outputs paths literally. Fix the test
to account both for escaped and literal backslash output.

[krytarowski]

In my opinion it's better to set UNSUPPORTED and align the NetBSD tar to GNU tar and libarchive.

[ruiu]

I thought NetBSD's tar is bsdtar because it's BSD... Anyways, I think I'm fine with this change, as the new test (which matches both foo\\.o and foo\.o) does not match a string that we don't want it to match.

[ruiu]

LGTM

We might be able to change NetBSD's tar but I guess that takes very long time. This test is not very important in the sense that this tests just test a corner case. So I think we should just land this to make it work on NetBSD.

[krytarowski]

bsdtar is libarchive (by BSD people too)

We can align our native tar later and land this as is.

lld/trunk/test/ELF/reproduce-backslash.s

 # REQUIRES: x86, shell
 
 # Test that we don't erroneously replace \ with / on UNIX, as it's
 # legal for a filename to contain backslashes.
 # RUN: llvm-mc %s -o %T/foo\\.o -filetype=obj -triple=x86_64-pc-linux
 # RUN: ld.lld %T/foo\\.o --reproduce %T/repro.tar -o /dev/null
 # RUN: tar tf %T/repro.tar | FileCheck %s
 
-# CHECK: repro/{{.*}}/foo\\.o
+# CHECK: repro/{{.*}}/foo\{{[\]?}}.o