buildroot

zsh: bump to version 5.4.2

Upstream does not provide a .tar.xz archive for this release. Revert to
.tar.gz.

Cc: Phil Eichinger <phil.eichinger@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>