[gnome-photos] build: Don't distribute git.mk

[Debarshi Ray <debarshir src gnome org>]

commit 9ed2c0763af25791e01e4c381f4e652ac15b0e98
Author: Debarshi Ray <debarshir gnome org>
Date:   Tue Oct 27 11:46:00 2015 +0100

    build: Don't distribute git.mk
    
    Use the '-' prefix when including git.mk. Otherwise Automake will mark
    git.mk as a dependency of the Makefile and pull it into the tarball.

 tests/Makefile.am |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index ff7d6ce..f3f3b20 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -26,4 +26,4 @@ EXTRA_DIST += \
        $(NULL)
 endif
 
-include $(top_srcdir)/git.mk
+-include $(top_srcdir)/git.mk