Makefile: Ensure rpm packages can be read by older rpm versions

The kernel.org hosts where the packages are built are now using Fedora
11, which defaults to sha256 for file digests instead of md5.  Older
versions of rpm can not handle these packages.  Tell rpmbuild to use md5
file digests for better compatibility.

Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -1799,7 +1799,10 @@ dist: git.spec git-archive$(X) configure
 	gzip -f -9 $(GIT_TARNAME).tar
 
 rpm: dist
-	$(RPMBUILD) -ta $(GIT_TARNAME).tar.gz
+	$(RPMBUILD) \
+		--define "_source_filedigest_algorithm md5" \
+		--define "_binary_filedigest_algorithm md5" \
+		-ta $(GIT_TARNAME).tar.gz
 
 htmldocs = git-htmldocs-$(GIT_VERSION)
 manpages = git-manpages-$(GIT_VERSION)