math/lapack: fix post-patch target for math/atlas

When upgrading this port, I previously merged the post-patch with the
pre-configure target, and it was a mistake.
The patch target is used from math/atlas, and make.inc is needed.

PR: 257122
Reported by: alt2600 (at) icloud.com
MFH: 2021Q3

(cherry picked from commit b7eec409d5664a73725c392b83e4f2741c5ad33f)