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");
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<tr><td><span title='2022-01-11 11:47:42 +0530'>2022-01-11</span></td><td><a href='/guix/commit/gnu/services/ci.scm?id=c1f8dffa549edc0873c8b6956d9b288b51bea521'>services: laminar: Set LAMINAR_BIND_RPC environment variable.</a><span class='msg-avail'>...<span class='msg-tooltip'>Earlier, the bind-rpc field of &lt;laminar-configuration&gt; was not used at
all. This was a bug.

* gnu/services/ci.scm (laminar-shepherd-service): Use bind-rpc to set
LAMINAR_BIND_RPC environment variable.
</span></span></td><td>Arun Isaac</td></tr>
<tr><td><span title='2021-06-10 09:58:20 +0530'>2021-06-10</span></td><td><a href='/guix/commit/gnu/services/ci.scm?id=0d2cbd663214a8aa4ed8b8c7716fe3436801a9a5'>services: laminar: Create parent directory for unix socket.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/ci.scm (laminar-activation): New function.
(laminar-service-type): Extend activation-service-type with
laminar-activation.
</span></span></td><td>Arun Isaac</td></tr>
<tr><td><span title='2021-04-09 11:59:58 +0100'>2021-04-09</span></td><td><a href='/guix/commit/gnu/services/ci.scm?id=eda4bb4f16f74436b0caf1c584888c89b3c4c69b'>services: Add Laminar.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/ci.scm: New file.
* gnu/tests/ci.scm: New file.
* doc/guix.texi (Laminar): Document the Laminar service.
</span></span></td><td>Christopher Baines</td></tr>