Enable GSSAPI in darwin release builds

[liggitt]

hack/build-go.sh cmd/oc -tags=gssapi produces an oc client capable of speaking Kerberos.

However, the release builds (defined in origin.spec and hack/build-cross.sh) run on Linux, and are not able to cross-compile to Darwin AND perform a cgo-enabled build.

[enj]

I see 4 possible ways to approach this:

1. Use Travis' macOS builders to build oc with CI
2. On one of our macs, build github.com/apcera/gssapi with -buildmode=shared and use that binary on linux with CI for the darwin builds (not sure if this will work)
3. Create some type of dynamic runtime linking wrapper like github.com/alexbrainman/sspi but for gssapi and use this on darwin with CI
4. Build oc on our macs with no CI

[openshift-bot]

Issues go stale after 90d of inactivity.

Mark the issue as fresh by commenting /remove-lifecycle stale. Stale issues rot after an additional 30d of inactivity and eventually close. Exclude this issue from closing by commenting /lifecycle frozen.

If this issue is safe to close now please do so with /close.

/lifecycle stale

[enj]

/unassign

@stlaz @sttts @mfojtik