This would previously fail since arm64 binaries need to be downloaded.

To quote 'go help test':

The idiomatic way to disable test caching explicitly is to use -count=1

- Otherwise this fails on some of the omnibus builder images

https://gitlab.com/gitlab-org/gitlab-shell/-/merge_requests/718 will
make Go 1.19 the default for gitlab-shell. Per
https://github.com/golang/go/issues/51940, the dev.boringcrypto branch
no longer exists, and to support FIPS we need to pass along
`GOEXPERIMENT=boringcrypto`.

To do this, we just see if this `GOEXPERIMENT` is available with `go
version` rather than do some more complicated version-specific
comparison.

Since https://gitlab.com/gitlab-org/gitlab-shell/-/merge_requests/682,
Kerberos headers and libraries are needed to build gitlab-sshd.  If
they are not available, `make build` successfully compiles
`bin/gitlab-shell` but fails to build `bin/gitlab-sshd`. However,
running `make build` again would do nothing and appear to be succeed
because `bin/gitlab-shell` existed. This led to Omnibus GitLab quietly
dropping the `gitlab-sshd` binary, as seen in
https://gitlab.com/gitlab-org/omnibus-gitlab/-/merge_requests/6446#note_1265879416.

To ensure `make build` properly fails if `bin/gitlab-sshd` cannot
be built, we make the binary an explicit build target.

Changelog: changed