cad/verilator: Update 5.040 => 5.042, unbreak on i386

Changelogs:

• https://github.com/verilator/verilator/releases/tag/v5.042
• https://github.com/verilator/verilator/compare/v5.040...v5.042

• Clarify LICENSE

Approved by: yuri@ (maintainer, Mentor)
Differential Revision: https://reviews.freebsd.org/D53544