Fix recent build regression on Android

[finagolfin]

Bionic added execinfo.h last year, but only made the backtrace APIs available
for Android API 33 or later.

@3405691582, #881 also removed your OpenBSD check, but I see that OpenBSD recently added this header, mesonbuild/meson#11151, so the header check should suffice there?

@al45tair, you suggested this change, please review.

Here is the error message showing this failing on my Android CI, and the subsequent pull adding this change to my Android CI that fixed it, finagolfin/swift-android-sdk#112.

[3405691582]

#881 is probably fine for OpenBSD, since we're just changing headers at this point. (I really should do a build soon to confirm, but I'm a little behind on Swift stuff.)

[al45tair]

@swift-ci Please smoke test

[al45tair]

@swift-ci Please smoke test Windows platform

[finagolfin]

The Windows CI got stuck?

[finagolfin]

Wait a second, I screwed up my logic in the condition, will fix it.

[finagolfin]

@al45tair, your suggestion in the comment above was right in the first place. I was trying to make it less convoluted, but my reformulation was not correct.

[al45tair]

@swift-ci Please smoke test

[al45tair]

@swift-ci Please smoke test Windows platform

[finagolfin]

Windows CI failed at checkout, all others passed.

[al45tair]

@swift-ci Please smoke test windows platform

[finagolfin]

Gah, should have written this as if __has_include(<execinfo.h>) && !(defined(__ANDROID__) && __ANDROID_API__ < 33), which reads better, and is what I was trying to come up with a couple days ago but screwed up.

@al45tair, wdyt, worth another CI run to rewrite this?

[al45tair]

Up to you. I don't mind either way. Add another commit to get it how you want it and I'll trigger CI again for you.

[finagolfin]

Alright, rewrote it, one last CI run and this can go in.

[al45tair]

@swift-ci Please smoke test

[al45tair]

@swift-ci Please smoke test Windows platform

[finagolfin]

@al45tair, this one and apple/swift#66745 are ready for merge.