Makefile.dist-packaging: fix make rpm with submodules

Makefile.dist-packaging seems to assume to be run under packaging/ as
"make -C packaging -f Makefile.dist-packaging rpm" so ensure the
srcdir is set correctly to point to the parent directory.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

packaging/Makefile.dist-packaging

@@ -3,7 +3,7 @@
 GITREV = $$(git describe --always --tags)
 GITREV_FOR_PKG = $(shell echo "$(GITREV)" | sed -e 's,-,\.,g' -e 's,^v,,')
 
-srcdir=$(shell pwd)
+srcdir=$(shell dirname `pwd`)
 PACKAGE=ostree
 
 PKG_VER = $(PACKAGE)-$(GITREV_FOR_PKG)
@@ -30,4 +30,4 @@ srpm: dist-snapshot
 	 ./rpmbuild-cwd -bs $(PACKAGE).spec
 
 rpm: srpm
-	$(srcdir)/rpmbuild-cwd --rebuild $(PKG_VER)*.src.rpm
+	./rpmbuild-cwd --rebuild $(PKG_VER)*.src.rpm