There's a merged pull request on the void-packages repository

nmap: revert to 7.80 due to licensing issues
https://github.com/void-linux/void-packages/pull/27866

Description:
nmap >= 7.90 is distributed under a modified license that many consider
problematic.

https://github.com/nmap/nmap/issues/2199
Gentoo bug: https://bugs.gentoo.org/749390
Debian bug: https://bugs.debian.org/972216
Guix discussion: https://lists.gnu.org/archive/html/guix-devel/2020-10/msg00227.html

Along, link against libssh2 instead of using the bundled version.