CI: Flush the CPAN cache if /usr/bin/perl has been updated since

CI: Flush the CPAN cache if /usr/bin/perl has been updated since
the cache was built. Possible fix for 2.4.x failure seen here:

https://github.com/apache/httpd/actions/runs/11322484507/job/31483266212

SSLeay.c: loadable library and perl binaries are mismatched (got first handshake key 0xeb00080, needed 0xf380080)

perldiag(1) describes this as a mismatch between libraries and binaries,
likely solved by reinstalling XS modules:

https://github.com/Perl/perl5/blob/77b78882c76e7461ccc4dcf2eb3afb9644836a72/pod/perldiag.pod#L3617

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1921307 13f79535-47bb-0310-9956-ffa450edef68