[geary] Add some more debian build cruft to .gitignore.

[Michael Gratton <mjog src gnome org>]

commit aba9be0d94b425f975a292b1f912ea82a0b3cfa7
Author: Michael James Gratton <mike vee net>
Date:   Thu Dec 14 09:54:54 2017 +1100

    Add some more debian build cruft to .gitignore.

 .gitignore |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/.gitignore b/.gitignore
index b8881d7..cf904a7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,6 +5,7 @@
 build/
 debian/*.debhelper.log
 debian/*.substvars
+debian/.debhelper
 debian/debhelper-build-stamp
 debian/files
 debian/geary