OpenSSL::config: Fix VMS guesses

OpenSSL::config: Fix VMS guesses

The MACHINE value from POSIX::uname() isn't trustworthy at all.
MACHINE names like this has been seen:

    _HP__VMM___(1.67GHz/9.0MB)

Perl's `$Config{archname}` is much more trustworthy, especially since
VMS isn't a multiarch operating system, at least yet.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19285)

(cherry picked from commit e63f5fdcb2658961f29fe7bed7968c0dcf7328a7)