libspice-server uses autotools and utilizes PKG_CHECK_MODULES to get openssl CFLAGS and LDFLAGS.
However, as we support various openssl flavors, including openssl from base that lacks pkg-config file, we
explicitly pass OPENSSL_LIBS and OPENSSL_CFLAGS via CONFIGURE_ENV, however, libspice-server
still adds 'openssl' package to Requires.private of its .pc file.

This causes a problem for software that requires libspice-server, because e.g. when using openssl from base,
detection will fail because .pc file is listing non-existent 'openssl' package.

To fix that, update libspice-server's configure.ac to add 'openssl' to Requires.private only if OPENSSL_LIBS and OPENSSL_CFLAGS wasn't explicitly specified by user, otherwise omit 'openssl' and just add the value of OPENSSL_LIBS to Libs.private.

While here, add 'amd64' to list of x86_64 cpus so it don't show a warning.