[source] gitignore: add /overlay

[LEDE Commits]

neoraider pushed a commit to source.git, branch master:
https://git.lede-project.org/b02636fcb4b16d437442f817a60a30e9b7ce4ed2

commit b02636fcb4b16d437442f817a60a30e9b7ce4ed2
Author: Matthias Schiffer <mschiffer at universe-factory.net>
AuthorDate: Sun Jan 15 18:16:29 2017 +0100

    gitignore: add /overlay
    
    Similar to /files, /overlay is only useful for modifications not tracked in
    the LEDE repository itself.
    
    Signed-off-by: Matthias Schiffer <mschiffer at universe-factory.net>
---
 .gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.gitignore b/.gitignore
index cd86e34..aff13e1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,6 +13,7 @@
 /feeds
 /feeds.conf
 /files
+/overlay
 /package/feeds
 /package/openwrt-packages
 key-build*