Cannot build lalsuite tarballs on ARCCA/Hawk because of ustar tar format restrictions on UID

The new ARCCA-Hawk computing centre in Cardiff assigns user and group IDs that are extremely large, e.g:

$ id
uid=100002171(duncan.macleod) gid=100002171(duncan.macleod) groups=100002171(duncan.macleod),6000005(LIGO)

These IDs exceed the limit of 2097151 allowed by the ustar tar format [1], meaning ./configure for lalsuite thinks that there isn't a usable tar and assigns false as the executable.

The two ways around this are:

1. reassign {U,G}IDs on Hawk to be lower than the ustar limit,

2. modify LALSuite to use the posix (pax) tar format, which allows unlimited UID and GID, but cannot be used on some systems, see the following excerpt from the automake docs [2]

   tar-pax selects the new pax interchange format defined by POSIX 1003.1-2001. It does not limit the length of file names. However, this format is very young and should probably be restricted to packages that target only very modern platforms. As of 2018, this format is supported by the native tar command only on GNU, FreeBSD, OpenBSD system; it is not supported by the native tar command on NetBSD, AIX, HP-UX, Solaris. There are moves to change the pax format in an upward-compatible way, so this option may refer to a more recent version in the future.

@adam-mercer, how disruptive would it be to modify lalsuite to use the posix tar format?

/cc @paul-hopkins