Dependency on ccache in postgresql17-devel-17.5-1PGDG.rhel9

Hi all,

I just tried recompiling an extension against PG 17.5 (via PGXS) and found
that I'm getting a new error from rpmbuild.

> make: /usr/lib64/ccache/clang: No such file or directory

I think this is the same problem that was reported in this thread
https://www.postgresql.org/message-id/flat/CA%2BmZaON9nDxWrg%3DABBczU3DuYwQ3Q02atsY%2BXhb0ogAgHzmYVg%40mail.gmail.com

The problem evaporates when I downgrade to 17.4, and I think it's the
change in the value for the CLANG variable in Makefile.global (previously
/usr/bin/clang, now /usr/lib64/ccache/clang).

Thanks,
Zane