Revert "Mac: Rebuild GMP to work around PIE deficiency"
Revert "Mac: Rebuild GMP to work around PIE deficiency"

This reverts commit 1e1f78a957af40ceead28332943f69d71f0858ed.

The workaround is no longer needed since the version 6
external_deps package has a correctly built GMP.

Unvanquished/release-scripts