Add $EUDEV_RULES_DIRECTORY to the list of rules directories.

The old udev 182 supported $UDEV_CONFIG_FILE, which in turn allowed
the search path to be customized, but eudev no longer has this, hence
this hack.

--- eudev-3.1.5/src/udev/udev-rules.c	2015-10-13 06:22:14.000000000 +0800
+++ eudev-3.1.5/src/udev/udev-rules.c	2015-10-16 20:45:38.491934336 +0800
@@ -47,15 +47,11 @@
         };
 };
 
-static const char* const rules_dirs[] = {
+static const char* rules_dirs[] = {
         UDEV_CONF_DIR "/rules.d",
         UDEV_RULES_DIR,
-        UDEV_ROOT_RUN "/udev/rules.d",
         UDEV_LIBEXEC_DIR "/rules.d",
-#ifdef HAVE_SPLIT_USR
-        "/lib/udev/rules.d",
-        "/usr/lib/udev/rules.d",
-#endif
+        NULL,			/* placeholder for $EUDEV_RULES_DIRECTORY */
         NULL};
 
 struct udev_rules {
@@ -1704,6 +1700,9 @@
 
         udev_rules_check_timestamp(rules);
 
+        /* Allow the user to specify an additional rules directory.  */
+        rules_dirs[3] = getenv("EUDEV_RULES_DIRECTORY");
+
         r = conf_files_list_strv(&files, ".rules", NULL, rules_dirs);
         if (r < 0) {
                 log_error_errno(r, "failed to enumerate rules files: %m");
og/tests/guix-hash.sh'>log</a><a href='/guix/tree/tests/guix-hash.sh?id=36045fa6d6f6ed240bf26d3040846533e9e35e82'>tree</a><a href='/guix/commit/tests/guix-hash.sh?id=36045fa6d6f6ed240bf26d3040846533e9e35e82'>commit</a><a href='/guix/diff/tests/guix-hash.sh?id=36045fa6d6f6ed240bf26d3040846533e9e35e82'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/guix-hash.sh'>
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<div class='path'>path: <a href='/guix/log/?id=36045fa6d6f6ed240bf26d3040846533e9e35e82'>root</a>/<a href='/guix/log/tests?id=36045fa6d6f6ed240bf26d3040846533e9e35e82'>tests</a>/<a href='/guix/log/tests/guix-hash.sh?id=36045fa6d6f6ed240bf26d3040846533e9e35e82'>guix-hash.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-hash.sh?id=36045fa6d6f6ed240bf26d3040846533e9e35e82&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-09-28 21:06:36 -0500'>2020-09-28</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=d8934360d2453a403b5433e71d09188e4ed23b57'>tests: Simplify shell exit status negation;</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/guix-archive.sh, tests/guix-build-branch.sh, tests/guix-build.sh,
tests/guix-daemon.sh, tests/guix-download.sh, tests/guix-environment.sh,
tests/guix-gc.sh, tests/guix-git-authenticate.sh, tests/guix-graph.sh,
tests/guix-hash.sh, tests/guix-lint.sh, tests/guix-pack-relocatable.sh,
tests/guix-pack.sh, tests/guix-package-aliases.sh, tests/guix-package-net.sh,
tests/guix-package.sh: Use the shell '!' keyword to negate command exit status
in place of 'if ...; then false; else true; fi'
</span></span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2020-05-22 00:35:24 +0200'>2020-05-22</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=0e4e9c8e7655f3e2a9c2615923768d211ac02a3e'>guix hash, guix download: Support base64 format.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/download.scm (show-help, %options): Support "base64"
format.
* guix/scripts/hash.scm (show-help, %options): Likewise.
* tests/guix-hash.sh: Test it.
* doc/guix.texi (Invoking guix hash): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-22 00:35:24 +0200'>2020-05-22</span></td><td><a href='/guix/commit/tests/guix-hash.sh?id=18ae1ec3ecfe22d55d6cdf595a442afebbc5595a'>guix hash, guix download: Add '--hash'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/download.scm (%default-options): Add 'hash-algorithm'.
(show-help, %options): Add "--hash".
(guix-download): Honor it.
* guix/scripts/hash.scm (%default-options): Add 'hash-algorithm'.
(show-help, %options): Add "--hash".
(guix-hash): Honor it.
* tests/guix-hash.sh: Test '-H sha512'.
* doc/guix.texi (Invoking guix download): Document it.
(Invoking guix hash): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>