Makefile: Add rootfs.tar.gz rule
Makefile: Add rootfs.tar.gz rule

For creating a tarball that can be committed to version control.  Git
just tracks the executable bit (not the file owner etc.), so using a
tarball is easier than restoring that stuff after clones and
checkouts.

Signed-off-by: W. Trevor King <f75897670c17327c42ab201733fb8a81ff9f4c34@tremily.us>

hmeng-19/ocitools,opencontainers/ocitools,wking/ocitools-v2,opencontainers/runtime-tools,hmeng-19/ocitools,liangchenye/ocitools,opencontainers/runtime-tools,opencontainers/ocitools,liangchenye/ocitools,wking/ocitools-v2