Avoid empty lines in nmake rule bodies

Avoid empty lines in nmake rule bodies

nmake is tolerant of those empty lines, but jom isn't.  That tolerance
isn't standard make behaviour, so we lean towards avoiding them.

We simply use '@rem' instead.

Fixes #16014

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16048)