util/perl/OpenSSL/config.pm: Rework determining compiler information
determine_compiler_settings() has been refactored to:
- find a compiler if none has been given by the user
- allow platform specific overrides, but only when the user didn't
already specify a desired compiler
- figure out the compiler vendor and version, making sure that the
version number is deterministic
- gather platform specific compiler information
Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11230)