YR Chen authored Mar 25, 2023 and Brad King committed Mar 28, 2023

The `-wmo` flag added by commit 6063428d (Swift: Update default build
flags, 2022-10-03, v3.26.0-rc1~585^2~1) behaves differently with the old
driver.  Detect when the old driver is being used, and avoid adding that
flag.

Fixes: #24641