Libarchive build failure with Glibc 2.36 on Linux

[Nathan Fisher <nfisher.sr%gmail.com@localhost>]

Glibc 2.36 has conflicting definitions of enum fsconfig_command in both 
linux/mount.h and sys/mount.h. This causes a build failure in libarchive 
as well as causing pkgsrc to fail to bootstrap due to libarchive being a 
dependency of several tools.

This can be worked around by removing the include for linux/fs.h in the 
file archive_read_disk_posix.c. However I would not be surprised if this 
needs to be conditional in order to not break other platforms or Glibc 
versions.

Thanks,
Nate