Support the PURPLE_PLUGIN_PATH environment variable.  This patch is based on
one from Nixpkgs, but properly handles the case where that variable is unset.

--- pidgin-2.10.11/libpurple/plugin.c.orig	2014-11-23 11:41:25.000000000 -0500
+++ pidgin-2.10.11/libpurple/plugin.c	2015-08-04 14:31:02.257366144 -0400
@@ -1178,8 +1178,19 @@
 void
 purple_plugins_init(void) {
 	void *handle = purple_plugins_get_handle();
+	const gchar *purple_plugin_path;
 
 	purple_plugins_add_search_path(LIBDIR);
+	purple_plugin_path = g_getenv("PURPLE_PLUGIN_PATH");
+	if (purple_plugin_path && *purple_plugin_path) {
+		gchar **paths = g_strsplit(purple_plugin_path, ":", -1);
+		if (paths) {
+			gchar **p;
+			for (p = paths; *p; ++p)
+				if (**p) purple_plugins_add_search_path(*p);
+		}
+		g_strfreev(paths);
+	}
 
 	purple_signal_register(handle, "plugin-load",
 						 purple_marshal_VOID__POINTER,
it' value='switch'/></form></td></tr>
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<tr><td><span title='2021-06-30 21:34:26 +0200'>2021-06-30</span></td><td><a href='/guix/commit/gnu/installer/newt/services.scm?id=6f13881f1e92832023caadb3cb51ce393e685e58'>installer: Offer the CUPS printing service.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/services.scm (%system-services): Add CUPS.
* gnu/installer/newt/services.scm (run-other-services-cbt-page):
New procedure.
(run-services-page): Call it last.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2021-01-31 17:08:17 +0100'>2021-01-31</span></td><td><a href='/guix/commit/gnu/installer/newt/services.scm?id=d09831fe52d0703ac912f191afb9b436738c09f8'>installer: Edit desktop selection prompt.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/newt/services.scm (run-desktop-environments-cbt-page):
Fix and clarify the #:info-text.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-10-23 16:35:38 +0200'>2020-10-23</span></td><td><a href='/guix/commit/gnu/installer/newt/services.scm?id=bfb65a676852755e6a608abc4d6cfe1f2f6471ac'>installer: Make the network management selection window tighter.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/newt/services.scm (run-network-management-page): Pass
 #:listbox-height.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-10-13 21:17:40 +0200'>2020-10-13</span></td><td><a href='/guix/commit/gnu/installer/newt/services.scm?id=1197b8b20f4fca4ce03bbc5fa75e18d54e3717c0'>installer: Add Emacs EXWM desktop environment.</a><span class='msg-avail'>...<span class='msg-tooltip'>Suggested by zenny via IRC.

* gnu/installer/services.scm (%system-services): Add emacs, emacs-exwm,
emacs-desktop-environment.
* etc/release-manifest.scm (%system-packages): Likewise.
* gnu/system/examples/lightweight-desktop.tmpl: Likewise.
* gnu/tests/install.scm (installation-target-desktop-os-for-gui-tests)
[packages]: Likewise
* gnu/installer/newt/services.scm (run-desktop-environments-cbt-page): Make
one entry taller.
</span></span></td><td>Jan (janneke) Nieuwenhuizen</td></tr>