From eed58cc443c2313a8b5fea94bcc6ccac16f63848 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Mon, 22 Sep 2025 10:58:29 +0100
Subject: [PATCH] build: Add $(NULL) as a convenient list terminator

When building lists of things in Makefiles it's convenient to have a
list terminator to avoid hanging backslash problems.  eg:

  EXTRA_DIST = \
           thing1 \
           thing2 \
           $(NULL)

Cherry picked from virt-v2v commit 09b86c07bf19beba9ccb8fcca0ebfae34dd56406
Cherry picked from guestfs-tools commit dad8c0d3803dcbc91e22ca35c630d9e8a01df81b
---
 common-rules.mk | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/common-rules.mk b/common-rules.mk
index 4df1e33f1..7a116c827 100644
--- a/common-rules.mk
+++ b/common-rules.mk
@@ -20,6 +20,10 @@
 
 -include $(top_builddir)/localenv
 
+# Convenient way to terminate lists in Makefiles, so that we avoid
+# problems with dangling backslashes.
+NULL =
+
 # Files that should universally be removed by 'make clean'.  Note if
 # there is any case in any subdirectory where a file should not be
 # removed by 'make clean', it should not be listed here!