make-git-snapshot: Use generated cargo vendor config

Nowadays it prints the result to stdout, so we can just use that
directly.

In particular, this fixes an issue for me where trying to use
direct `git` dependencies (not via crates.io) needs a separate
config stanza.

packaging/make-git-snapshot.sh

@@ -27,7 +27,8 @@ ls -al ${TARFILE_TMP}
     tar -A -f ${TARFILE_TMP} submodule.tar
     rm submodule.tar
 done
-tmpd=${TOP}/.dist-tmp
+disttmp=.dist-tmp
+tmpd=${TOP}/$disttmp
 trap cleanup EXIT
 function cleanup () {
     if test -f ${tmpd}/.tmp; then
@@ -40,9 +41,8 @@ mkdir ${tmpd} && touch ${tmpd}/.tmp
 
 (cd ${tmpd}
  mkdir -p .cargo vendor
- (cd ${TOP} && cargo vendor ${tmpd}/vendor)
+ (cd ${TOP} && cargo vendor ${tmpd}/vendor | sed -e "s,^directory *=.*,directory = './vendor',") > .cargo/config
  cp ${TOP}/Cargo.lock .
- cp ${TOP}/cargo-vendor-config .cargo/config
  # Filter out bundled libcurl and systemd; we always want the pkgconfig ones
  for crate_subdir in curl-sys/curl \
                      libz-sys/src/zlib \