[cmake] Improve the OSX cross build flags

Summary: Since D17266 we no longer need to pass the -B flag. Also reorder the args to make it more logical and rename LD64 to LLD.

Test Plan: Run the guix osx build.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17275