Ignore config.cache

Change-Id: Ida2294e490eb5eec515aa00742fb6cfc29b11b48
Reviewed-on: https://gerrit.osmocom.org/83
Tested-by: Jenkins Builder
Reviewed-by: Holger Freyther <holger@freyther.de>
diff --git a/.gitignore b/.gitignore
index 32915aa..03ce379 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,6 +12,7 @@
 aminclude.am
 m4/*.m4
 autom4te.cache
+config.cache
 config.h*
 config.sub
 config.log