Configure: DON'T trickle down includes from products to sources

Instead, use the include settings from the products later in the process,
making it possible to have different includes for two different libraries
that share the same source code.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7159)