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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<div class='path'>path: <a href='/guix/log/?id=635bf73d2f1b5e8bd913de4e673273a39830a7c2'>root</a>/<a href='/guix/log/gnu?id=635bf73d2f1b5e8bd913de4e673273a39830a7c2'>gnu</a>/<a href='/guix/log/gnu/packages?id=635bf73d2f1b5e8bd913de4e673273a39830a7c2'>packages</a>/<a href='/guix/log/gnu/packages/nvi.scm?id=635bf73d2f1b5e8bd913de4e673273a39830a7c2'>nvi.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/packages/nvi.scm?id=635bf73d2f1b5e8bd913de4e673273a39830a7c2&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-01-23 23:28:57 +0100'>2020-01-23</span></td><td><a href='/guix/commit/gnu/packages/nvi.scm?id=3440fecd4eff3bde98a4ffe7ad241f2b23ba1f5f'>gnu: nvi: Fix build with glibc 2.30.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/nvi.scm (nvi)[source](modules): New field.
[source](snippet): Add substitution to prevent including code that relies on
obsolete glibc functions.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-01-16 16:08:22 +0100'>2019-01-16</span></td><td><a href='/guix/commit/gnu/packages/nvi.scm?id=255d1bbe777a824be726edeb9fd47458a3a877a9'>gnu: Move dbm databases to new module.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/databases.scm (gdbm, bdb, bdb-5.3): Move from here...
* gnu/packages/dbm.scm: ...to this new module.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* gnu/packages/audio.scm,
gnu/packages/avahi.scm,
gnu/packages/backup.scm,
gnu/packages/cobol.scm,
gnu/packages/cyrus-sasl.scm,
gnu/packages/databases.scm,
gnu/packages/finance.scm,
gnu/packages/game-development.scm,
gnu/packages/gnome.scm,
gnu/packages/guile.scm,
gnu/packages/ibus.scm,
gnu/packages/kerberos.scm,
gnu/packages/linux.scm,
gnu/packages/mail.scm,
gnu/packages/man.scm,
gnu/packages/nvi.scm,
gnu/packages/openldap.scm,
gnu/packages/package-management.scm,
gnu/packages/php.scm,
gnu/packages/pulseaudio.scm,
gnu/packages/python.scm,
gnu/packages/rdf.scm,
gnu/packages/ruby.scm,
gnu/packages/sawfish.scm: Update module references.
</span></span></td><td>Ricardo Wurmus</td></tr>