Set EV_BACKENDS_DIR to the backends directory of evince

Closes #13309
(grafted from 190fb5c8b47039b26c4870ec45c332fe6b7e5409)

--HG--
branch : 6.0

tryton/bin/tryton

@@ -18,7 +18,8 @@ if hasattr(sys, 'frozen'):
     share = os.path.join(prefix, 'share')
     os.environ['GTK_EXE_PREFIX'] = prefix
     os.environ['GTK_DATA_PREFIX'] = prefix
-    os.environ['EV_BACKENDS_DIR'] = prefix
+    os.environ['EV_BACKENDS_DIR'] = os.path.join(
+        prefix, 'lib', 'evince', '4', 'backends')
     os.environ['XDG_DATA_DIRS'] = share
     os.environ['GDK_PIXBUF_MODULE_FILE'] = os.path.join(
             share, 'gtk-3.0', 'gdk-pixbuf.loaders')