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

Patch borrowed/adapted from Nixpkgs.

--- perl-5.16.1/cpan/Module-Pluggable/lib/Module/Pluggable/Object.pm	2015-04-08 23:28:48.120164135 -0500
+++ perl-5.16.1/cpan/Module-Pluggable/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;
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<div class='path'>path: <a href='/guix/log/?id=bca1496f7290a0ae9a0186f325f3806b6209e6c3'>root</a>/<a href='/guix/log/tests?id=bca1496f7290a0ae9a0186f325f3806b6209e6c3'>tests</a>/<a href='/guix/log/tests/search-paths.scm?id=bca1496f7290a0ae9a0186f325f3806b6209e6c3'>search-paths.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/search-paths.scm?id=bca1496f7290a0ae9a0186f325f3806b6209e6c3&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-06-14 22:09:38 +0200'>2019-06-14</span></td><td><a href='/guix/commit/tests/search-paths.scm?id=92d00ca4661e186022732a47956a2bc0ef16be96'>build: Remove 'gnu/packages/bootstrap' and its binaries.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-04-04 00:10:00 +0200'>2017-04-04</span></td><td><a href='/guix/commit/tests/search-paths.scm?id=f73bb91ebe8d78f54bb90d2168b353a4f5210f02'>tests: Adjust search-paths test following the introduction of aarch64.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-01-23 22:23:41 +0100'>2017-01-23</span></td><td><a href='/guix/commit/tests/search-paths.scm?id=fcd75bdbfa99d14363b905afbf914eec20e69df8'>search-paths: Allow specs with #f as their separator.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>