benchmarks/vkoverhead: exorcise -Werror and unbreak on armv7

This fixes the build on armv7, avoiding a bogus int conversion
warning. While we are at it, turn static REINPLACE_CMD usage
into patch file as per policy.

Approved by: portmgr (build fix blanket)
MFH: 2025Q4

(cherry picked from commit f95a776840b0d53d446a8f219ed6ed5a7b135029)