Raul Tambre authored Nov 10, 2022 and Brad King committed Nov 10, 2022

Compile with the preprocessor definitions necessary for the `arc4random`
family so it's available even when compiler extensions are not enabled.
Similar things are done in cmbzip2, cmcurl, cmlibarchive, cmliblizma and
cmlibuv.

This issue surfaced on a nightly bot after glibc 2.36 added arc4random
functions. cmlibarchive defines the necessary macro, but also relies on
`HAVE_ARC4RANDOM_BUF`.  cmlibarchive's check with the necessary macro
defined was skipped due to cmexpat running the same check before, but
without the macros, and it being cached.

This extends commit c7c3e39e (Utilities: Activate POSIX APIs even
without compiler extensions, 2022-06-02, v3.24.0-rc1~34^2) to cover our
build of expat too.

Issue: #20454