Skip tests that rely on unlinkat(2) behavior that varies between
kernel versions and is unspecified.

See <http://bugs.gnu.org/20597>
and <http://lists.gnu.org/archive/html/bug-tar/2015-06/msg00000.html>.

--- tar-1.28/tests/testsuite	2014-07-27 22:35:27.000000000 +0200
+++ tar-1.28/tests/testsuite	2015-06-16 00:21:16.906380739 +0200
@@ -34680,6 +34680,7 @@ find .
 )"
 at_fn_check_prepare_notrace 'an embedded newline' "remfiles08a.at:31"
 ( $at_check_trace;
+exit 77
 mkdir gnu
 (cd gnu
 TEST_TAR_FORMAT=gnu
@@ -34762,6 +34763,7 @@ find .
 )"
 at_fn_check_prepare_notrace 'an embedded newline' "remfiles08b.at:36"
 ( $at_check_trace;
+exit 77
 mkdir gnu
 (cd gnu
 TEST_TAR_FORMAT=gnu
@@ -34850,6 +34852,7 @@ find .
 )"
 at_fn_check_prepare_notrace 'a `...` command substitution' "remfiles08c.at:31"
 ( $at_check_trace;
+exit 77
 mkdir gnu
 (cd gnu
 TEST_TAR_FORMAT=gnu
value='switch'/></form></td></tr>
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<div class='path'>path: <a href='/guix/log/?id=8cc13fcff534e4a8f37d675fed215a265bdaeb4e'>root</a>/<a href='/guix/log/tests?id=8cc13fcff534e4a8f37d675fed215a265bdaeb4e'>tests</a>/<a href='/guix/log/tests/guix-environment.sh?id=8cc13fcff534e4a8f37d675fed215a265bdaeb4e'>guix-environment.sh</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/guix-environment.sh?id=8cc13fcff534e4a8f37d675fed215a265bdaeb4e&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-01-19 17:45:38 +0100'>2021-01-19</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=4d79f072cc7b502fc25486d514c9200ba684a596'>environment: Fix '--root' option with relative file name.</a><span class='msg-avail'>...</span></td><td>JOULAUD François</td></tr>
<tr><td><span title='2020-09-28 21:06:36 -0500'>2020-09-28</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=d8934360d2453a403b5433e71d09188e4ed23b57'>tests: Simplify shell exit status negation;</a><span class='msg-avail'>...</span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2019-11-22 15:07:58 +0100'>2019-11-22</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=d76df98fa59166c0c9f71ca41d664857d93e136d'>environment: Document that '--manifest' can be repeated.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-08-22 15:53:27 -0400'>2019-08-22</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=893c2df00daa4e6dd6a7ff3813d7df5329877f9e'>Merge branch 'master' into core-updates</a></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2019-08-17 16:23:05 +0200'>2019-08-17</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=75a6f66815db811cc41aadbe93033a6efd3ad62f'>tests: Move 'guix environment -C --no-cwd' test where it belongs.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-07-12 01:03:53 +0200'>2019-07-12</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=fb9a23a3f3ad3d7b5b7f03b2007baf27684d6bbd'>Merge branch 'master' into core-updates</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-07-08 10:33:20 -0400'>2019-07-08</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=b6dc08393e6a8313b88ce422fc3c1e4e9c0efc6f'>scripts: environment: Add --no-cwd.</a><span class='msg-avail'>...</span></td><td>Carl Dong</td></tr>
<tr><td><span title='2019-06-14 21:57:39 +0200'>2019-06-14</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=03d76577b96ba81c9921eb3a297d42db8644280b'>tests: Make builds less expensive.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-05-07 15:46:53 +0200'>2019-05-07</span></td><td><a href='/guix/commit/tests/guix-environment.sh?id=d108f59761f6581bff0d405c38852688ba04961d'>environment: Non ad-hoc mode also honors transformation options.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>