[gnome-builder] library-template: Add AM_V_GEN to the AUTHORS rule

[Philip Withnall <pwithnall src gnome org>]

commit 94c279505f3c94ce24bff71253ba9a8e9184f46d
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Sun Jan 31 11:19:26 2016 +0100

    library-template: Add AM_V_GEN to the AUTHORS rule
    
    This should expose it in the automake output so the user can see it’s
    been generated.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=761356

 .../library_template/shared-library/Makefile.am    |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/plugins/library-template/library_template/shared-library/Makefile.am 
b/plugins/library-template/library_template/shared-library/Makefile.am
index 56b9ab9..05ab2b6 100644
--- a/plugins/library-template/library_template/shared-library/Makefile.am
+++ b/plugins/library-template/library_template/shared-library/Makefile.am
@@ -9,7 +9,7 @@ SUBDIRS = \
 EXTRA_DIST = AUTHORS
 
 AUTHORS:
-       @if test -d "$(srcdir)/.git"; \
+       $(AM_V_GEN)if test -d "$(srcdir)/.git"; \
        then \
                echo Creating $@ && \
                ( cd "$(top_srcdir)" && \