[PATCH 5 of 5 remotefilelog-ext debs] Makefile: add `make deb` rule for convenience

[Augie Fackler]

# HG changeset patch
# User Augie Fackler <augie at google.com>
# Date 1441899102 14400
#      Thu Sep 10 11:31:42 2015 -0400
# Node ID 937116e5408258b3d359cc486218e966557aeed7
# Parent  9fec75539a1e42cee876b481f1e748dafc1f347c
Makefile: add `make deb` rule for convenience

This matches what Mercurial has, so I figure we may as well be
consistent.

diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -20,3 +20,6 @@ install:
 clean:
 	-$(PYTHON) setup.py clean --all # ignore errors from this command
 	find . \( -name '*.py[cdo]' -o -name '*.so' \) -exec rm -f '{}' ';'
+
+deb:
+	contrib/builddeb