current tools no longer build on 9.3

Hey,

It seems that an assumption has been made in lib/libc/time/zic.c where
HAVE_GETRANDOM is unconditionally defined for NetBSD builds. This
(linux, non-standard function with an amusingly scathing BUGS section in
the man page) function was introduced in 10.0 and causes builds on
earlier releases to fail tools.

The change seems to have been made in version 1.96 of the file in
december 2025.

Just removing the HAVE_GETRANDOM define seems to make it build on my 9.3
build system. I would hope that we don't consider netbsd-9 too obsolete
to build on... perhaps this could be __NetBSD_Version__ gated if it's
desired?

Cheers,
Staffan