patch 8.0.0277: the GUI test may trigger fontconfig and take a long time

Problem:    The GUI test may trigger fontconfig and take a long time.
Solution:   Set $XDG_CACHE_HOME. (Kazunobu Kuriyama)
diff --git a/src/version.c b/src/version.c
index 8aeb688..3aa1786 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    277,
+/**/
     276,
 /**/
     275,