build: don't force buildinfo to be remade at each build

Change-Id: I2a9bc46455f72c99e8d8101575d555597e614ea9
Reviewed-by: Philippe Gorley <philippe.gorley@savoirfairelinux.com>

src/Makefile.am

@@ -172,9 +172,3 @@ if RING_VIDEO
 nobase_include_HEADERS+= \
 		dring/videomanager_interface.h
 endif
-
-# Force buildinfo to be remade at each build
-buildinfo.cpp: FORCE
-	@touch buildinfo.cpp
-
-FORCE:;