The include search path was not picking up files in the root of the tree. [extended tests] Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/4316)
Don't build ossl_shim by default. Switch it on through enable-external-tests. Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org>