Segfault building devel/re2c on macOS

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Setting up a second M1 Mac, I suddenly get mysterious repeatable segfaults 
building certain packages, most notably devel/re2c. Since that's a dependency 
of ninja-build, quite a lot of my usual set fails.

Has anyone seen this? I'm on 11.6.2 and pkgsrc-current as of the day before 
yesterday. I bootstrapped with an older -current (I copied pkgsrc from another 
machine and couldn't update before bootstrapping due to lack of cvs).