gitignore: Ignore repo tool directory

This reduces the noise produced by 'git status' and 'repo status' when
orchestrating the layers with Google's repo tool
(https://gerrit.googlesource.com/git-repo/).

Signed-off-by: Christian Meusel <christian.meusel@posteo.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

.gitignore

@@ -2,6 +2,7 @@ bitbake
 *.pyc
 *.pyo
 /*.patch
+/.repo/
 /build*/
 pyshtables.py
 pstage/