8e841bd419
si_code in siginfo_t is a macro on NetBSD, not a member of the struct itself, so add a C trampoline for receiving its value. Also replace references to mos.waitsemacount with the replacement and add some helpers from os_netbsd.go in the GC repository. Update golang/go#38538. Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/228918