Fix treatment of BUILD_METADATA

Fix treatment of BUILD_METADATA

According to documentation [^1], the BUILD_METADATA from VERSION.dat should
be prefixed with a plus sign when used.  It is given this treatment in
Configure, but not in all other scripts that use VERSION.dat directly.
This change fixes that.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/19815)