This patch makes GTK+ look for additional modules in a list of directories
specified by the environment variable "GUIX_GTK3_PATH".  This can be used
instead of "GTK_PATH" to make GTK+ find modules that are incompatible with
other major versions of GTK+.

--- a/gtk/gtkmodules.c	2015-09-20 20:09:05.060590217 +0200
+++ b/gtk/gtkmodules.c	2015-09-20 20:10:33.423124833 +0200
@@ -52,6 +52,7 @@
 get_module_path (void)
 {
   const gchar *module_path_env;
+  const gchar *module_guix_gtk3_path_env;
   const gchar *exe_prefix;
   gchar *module_path;
   gchar *default_dir;
@@ -61,6 +62,7 @@
     return result;
 
   module_path_env = g_getenv ("GTK_PATH");
+  module_guix_gtk3_path_env = g_getenv ("GUIX_GTK3_PATH");
   exe_prefix = g_getenv ("GTK_EXE_PREFIX");
 
   if (exe_prefix)
@@ -68,7 +70,13 @@
   else
     default_dir = g_build_filename (_gtk_get_libdir (), "gtk-3.0", NULL);
 
-  if (module_path_env)
+  if (module_guix_gtk3_path_env && module_path_env)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk3_path_env, module_path_env, default_dir, NULL);
+  else if (module_guix_gtk3_path_env)
+    module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
+				module_guix_gtk3_path_env, default_dir, NULL);
+  else if (module_path_env)
     module_path = g_build_path (G_SEARCHPATH_SEPARATOR_S,
 				module_path_env, default_dir, NULL);
   else
gnu/machine?id=81ad759ab96a3bfb9801467b7182af6a2d13159d'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/machine'>
<input type='hidden' name='id' value='81ad759ab96a3bfb9801467b7182af6a2d13159d'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=81ad759ab96a3bfb9801467b7182af6a2d13159d'>root</a>/<a href='/guix/log/gnu?id=81ad759ab96a3bfb9801467b7182af6a2d13159d'>gnu</a>/<a href='/guix/log/gnu/machine?id=81ad759ab96a3bfb9801467b7182af6a2d13159d'>machine</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/machine?id=81ad759ab96a3bfb9801467b7182af6a2d13159d&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-09-04 17:57:02 +0200'>2022-09-04</span></td><td><a href='/guix/commit/gnu/machine?id=a451a809d5537035cc8888cfde5349842a68e934'>Fix misspelling of GUIX_DIGITAL_OCEAN_TOKEN.</a><span class='msg-avail'>...</span></td><td>Matthew James Kraai</td></tr>
<tr><td><span title='2022-03-01 10:30:17 -0500'>2022-03-01</span></td><td><a href='/guix/commit/gnu/machine?id=0dc019e19a23fea614be5623360849ab9bc35e74'>initrd: Use non-hyphenated kernel command-line parameter names.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-01-16 23:56:55 +0100'>2022-01-16</span></td><td><a href='/guix/commit/gnu/machine?id=084b76a70a6b302529f3450e6d07f1d105a10f7d'>machine: ssh: Add 'safety-checks?' field.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-01-09 23:17:17 +0100'>2022-01-09</span></td><td><a href='/guix/commit/gnu/machine?id=7f20e59a13a6acc3331e04185b8f1ed2538dcd0a'>machine: ssh: Open a single SSH session per machine.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-08-29 01:05:26 -0400'>2021-08-29</span></td><td><a href='/guix/commit/gnu/machine?id=da4e40948326387d5bcda58783914d5f9ce8b095'>Migrate to the new 'targets' field of bootloader-configuration.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-06-20 16:44:08 +0200'>2021-06-20</span></td><td><a href='/guix/commit/gnu/machine?id=ef3f38ea0027f48feb6a29df131ac58bfbb46b7d'>services: openssh: Replace 'without-password' by 'prohibit-password'.</a><span class='msg-avail'>...</span></td><td>Brice Waegeneire</td></tr>
<tr><td><span title='2021-06-03 13:04:20 +0200'>2021-06-03</span></td><td><a href='/guix/commit/gnu/machine?id=fe509e017fa1c0e3d0b057784b081def3aa621ad'>machine: ssh: Respect calling convention for monadic procedures.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-06-01 23:26:07 +0200'>2021-06-01</span></td><td><a href='/guix/commit/gnu/machine?id=2885c3568edec35086f8feeae5b60259cbea407c'>machine: ssh: Gracefully handle failure of the effectful bits.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-02-25 11:29:35 +0100'>2021-02-25</span></td><td><a href='/guix/commit/gnu/machine?id=120051e1b9358f75b228e97670843095d5fcdf49'>machine: ssh: Use 'formatted-message'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-01-04 11:51:48 +0100'>2021-01-04</span></td><td><a href='/guix/commit/gnu/machine?id=61d8bd56a4644a72b964b680456da4332eb1ef6d'>machine: ssh: Do not import the host (guix config), really.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-12-21 18:41:11 +0100'>2020-12-21</span></td><td><a href='/guix/commit/gnu/machine?id=f00e68ace070fd5240a4b5874e61c26f6e909b6c'>system: Allow separated /boot and encrypted root.</a><span class='msg-avail'>...</span></td><td>Miguel Ángel Arruga Vivas</td></tr>