make-release: only leave tarball of wrap-file subprojects

make-release: only leave tarball of wrap-file subprojects

The QEMU source archive is including the sources downloaded from crates.io
in both tarball form (in subprojects/packagecache) and expanded/patched
form (in the subprojects directory).  The former is the more authoritative
form, as it has a hash that can be verified in the wrap file and checked
against the download URL, so keep that one only.  This works also with
--disable-download; when building QEMU for the first time from the
tarball, Meson will print something like

    Using proc-macro2-1-rs source from cache.

for each subproject, and then go on to extract the tarball and apply the
overlay or the patches in subprojects/packagefiles.

Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2719
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>