1. Enable build from dist tarball independent of git.

     In current master branch of vpp version, we  use "make pkg-rpm" command to build a rpm, which may be break down if "git rev-parse 2> /dev/null" case return "0".

     As codes show below:

DIST_FILE = $(BR)/vpp-$(shell src/scripts/version).tar
DIST_SUBDIR = vpp-$(shell src/scripts/version|cut -f1 -d-)

dist:
@if git rev-parse 2> /dev/null ; then \
git archive \
--prefix=$(DIST_SUBDIR)/ \
--format=tar \
-o $(DIST_FILE) \
HEAD ; \
git describe > $(BR)/.version ; \
else \
(cd .. ; tar -cf $(DIST_FILE) $(DIST_SUBDIR) --exclude=*.tar) ; \
src/scripts/version > $(BR)/.version ; \
fi

   The path "DIST_SUBDIR" needs to be created before running 'tar' command, that is because  'tar'command can not compress files from a non-existent path.

    Errors show:

tar: vpp-17.10: Cannot stat: No such file or directory
tar: Exiting with failure status due to previous errors

2. Fix bug

     In order to fix this bug, we should to create the path "DIST_SUBDIR" at fist, and, copy source codes into the "DIST_SUBDIR" . After these steps, we can get a whole tarball to build rpm.