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
witch'/></form></td></tr>
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<div class='path'>path: <a href='/guix/log/?id=9dea3f101f252331c049c03f501398a5ec837ba9'>root</a>/<a href='/guix/log/gnu?id=9dea3f101f252331c049c03f501398a5ec837ba9'>gnu</a>/<a href='/guix/log/gnu/services?id=9dea3f101f252331c049c03f501398a5ec837ba9'>services</a>/<a href='/guix/log/gnu/services/hurd.scm?id=9dea3f101f252331c049c03f501398a5ec837ba9'>hurd.scm</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/gnu/services/hurd.scm?id=9dea3f101f252331c049c03f501398a5ec837ba9&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-06-13 10:04:51 +0200'>2020-06-13</span></td><td><a href='/guix/commit/gnu/services/hurd.scm?id=7304cb0a23a11b68d98ee70d911adc7048900536'>services: hurd: Remove deprecated 'hurd-getty-service' wrapper.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/hurd.scm (hurd-getty-service): Remove.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>
<tr><td><span title='2020-06-08 14:26:14 +0200'>2020-06-08</span></td><td><a href='/guix/commit/gnu/services/hurd.scm?id=7ccd471c71d650055e99cd02381bc8dcd86d5313'>services: Add `hurd-getty-service-type'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/hurd.scm (&lt;hurd-gettty-configuration&gt;): New record.
(hurd-ttys-shepherd-service): New procedure.
(hurd-getty-service-type): New variable.
* doc/guix.texi (Hurd Services): Document it.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>
<tr><td><span title='2020-06-08 14:26:14 +0200'>2020-06-08</span></td><td><a href='/guix/commit/gnu/services/hurd.scm?id=f9c04580bf5462bb088f47ad8fc6c3136649cbd6'>services: Add `hurd-console-service-type'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/hurd.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Hurd Services): Document it.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>