siteinfo: Move apr configure cache to common-linux

siteinfo: Move apr configure cache to common-linux

There are variables which are used in all target specific
sitefiles. Move it to common-linux, so it can be effective
for all targets. Usually they will vary based upon libc
e.g. musl does not have process shared mutexes so apr_cv_process_shared_works
should be no for it. For glibc though it should be yes but
existing behaviour is to use 'no' so its left as it is.

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>