Unbreak Configure calls in cross builds

Upstream commit v5.23.5-89-g7a4fcb3f64 broke the way we pass cross build
related information to Configure via optdef.sh.

Use -Dvar=val command line arguments instead.

While at it, the -O (override) argument is no longer needed since
upstream commit v5.23.4-46-g41d73075f0.

Closes: #872471