Cross-compiling for Darwin or FreeBSD fails because of build constraints

[botherder]

While cross-compiling from a Debian dev machine to other platforms, building for Darwin and FreeBSD raises this issue instead:

go build github.com/hillu/go-yara/internal/callbackdata: build constraints exclude all Go files in $GOPATH/pkg/mod/github.com/hillu/[email protected]/internal/callbackdata

I've not been able to triage the issue entirely, although it sounds like it could be related to this? golang/go#24068

[botherder]

Nevermind, my mistake.

[hillu]

What kind of C cross-compiler setup are you using for FreeBSD and Darwin targets?