package/localedef: compile against glibc-2.29

In glibc 2.27 the following change occurred:
"Statically compiled applications attempting to load locales compiled
for the GNU C Library version 2.27 will fail and fall back to the
builtin C/POSIX locale."

This impacts us since upstream buildroot uses a localdef built against
an older eglibc release, as reported at [0].

This is a combination of my patch to move to glibc and Peter Seiderer's
patch to avoid building all of glibc just for localedef.

 [0] https://bugs.busybox.net/show_bug.cgi?id=11096



Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
[localedef build & fixups:]
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
[Thomas: share the tarball with the glibc package]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>