Log Message:
libarchive: fix builds where __RCSID isn't defined by the OS

The 3.7.3 release removed all __FBSDID and __RCSID strings and support
for them. Evidently there was a merge botch with archive_pack_dev.c
where __RCSID was retained there in our copy, which breaks builds on
most OSes. Addresses PR pkg/58152 from Hiroshi Hakoyama.