Fix Perl module Module::Pluggable such that it can find plugins that live in
symlinked directories.

Patch borrowed/adapted from Nixpkgs.

--- Module-Pluggable-5.2/lib/Module/Pluggable/Object.pm   2015-04-08 23:28:48.120164135 -0500
+++ Module-Pluggable-5.2/lib/Module/Pluggable/Object.pm   2015-04-08 23:30:27.032166704 -0500
@@ -164,7 +164,7 @@
         my $sp = catdir($dir, (split /::/, $searchpath));

         # if it doesn't exist or it's not a dir then skip it
-        next unless ( -e $sp && -d _ ); # Use the cached stat the second time
+        next unless ( -e $sp );

         my @files = $self->find_files($sp);

@@ -279,7 +279,7 @@
                              (my $path = $File::Find::name) =~ s#^\\./##;
                              push @files, $path;
                            }
-                      }, $search_path );
+                      }, "$search_path/." );
     }
     #chdir $cwd;
     return @files;><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=2bc967e53dc6fd31f333485e614040581cd0052c'>refs</a><a class='active' href='/guix/log/tests/accounts.scm'>log</a><a href='/guix/tree/tests/accounts.scm?id=2bc967e53dc6fd31f333485e614040581cd0052c'>tree</a><a href='/guix/commit/tests/accounts.scm?id=2bc967e53dc6fd31f333485e614040581cd0052c'>commit</a><a href='/guix/diff/tests/accounts.scm?id=2bc967e53dc6fd31f333485e614040581cd0052c'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/accounts.scm'>
<input type='hidden' name='id' value='2bc967e53dc6fd31f333485e614040581cd0052c'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=2bc967e53dc6fd31f333485e614040581cd0052c'>root</a>/<a href='/guix/log/tests?id=2bc967e53dc6fd31f333485e614040581cd0052c'>tests</a>/<a href='/guix/log/tests/accounts.scm?id=2bc967e53dc6fd31f333485e614040581cd0052c'>accounts.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/tests/accounts.scm?id=2bc967e53dc6fd31f333485e614040581cd0052c&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-08-28 00:27:14 +0200'>2019-08-28</span></td><td><a href='/guix/commit/tests/accounts.scm?id=dd4e46edda6c255ca170a6650c6f92b16ff50a3f'>accounts: Delete duplicate entries.</a><span class='msg-avail'>...<span class='msg-tooltip'>When adding multiple instances of a service requiring some user
account/group, we could end up with multiple entries for that account or
group in /etc/passwd or /etc/group.

* gnu/build/accounts.scm (database-writer)[write-entries]: Add call to
'delete-duplicates'.
* tests/accounts.scm ("write-passwd with duplicate entry"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-04-27 16:30:40 +0200'>2019-04-27</span></td><td><a href='/guix/commit/tests/accounts.scm?id=0c329bf4b0c00abdc9a7d9c818d36d4d60b3005d'>tests: Adjust accounts test to shell-as-config change.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 504a0fc636ec591e65b4a229a37e522e425d8a0c.

* tests/accounts.scm ("allocate-passwd with previous state"): Change
expected 'shell' for "alice" to "/bin/sh".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-03-25 23:37:06 +0100'>2019-03-25</span></td><td><a href='/guix/commit/tests/accounts.scm?id=cf848cc0a17a3a58d600116896f6e7abfb0440d4'>accounts: Add default value for the 'home-directory' field of &lt;user-account&gt;.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/accounts.scm (&lt;user-account&gt;)[home-directory]: Mark as
thunked and add a default value.
(default-home-directory): New procedure.
* doc/guix.texi (User Accounts): Remove 'home-directory' from example.
* gnu/system/examples/bare-bones.tmpl: Likewise.
* gnu/system/examples/beaglebone-black.tmpl: Likewise.
* gnu/system/examples/desktop.tmpl: Likewise.
* gnu/system/examples/docker-image.tmpl: Likewise.
* gnu/system/examples/lightweight-desktop.tmpl: Likewise.
* gnu/system/install.scm (installation-os): Likewise.
* gnu/tests.scm (%simple-os): Likewise.
* gnu/tests/install.scm (%minimal-os, %minimal-os-on-vda):
(%separate-home-os, %encrypted-root-os, %btrfs-root-os): Likewise.
* tests/accounts.scm ("allocate-passwd")
("allocate-passwd with previous state"): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-03-07 20:05:09 +0100'>2019-03-07</span></td><td><a href='/guix/commit/tests/accounts.scm?id=ec600e4544729f1aaf46fa5162bba334515d0de5'>Add (gnu build accounts).</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/build/accounts.scm, tests/accounts.scm: New files.
* Makefile.am (SCM_TESTS): Add tests/accounts.scm.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add build/accounts.scm.
</span></span></td><td>Ludovic Courtès</td></tr>