Mark as BROKEN on aarch64: attempts to fetch files during build.

This may actually be an infrastructure error. It seems that the files
called out in GH_TUPLE are not being fetched in the fetch phase -- but
only on aarch64. (The amd64 fetch works.) Later, this causes the
following error:

===>  Building bapu from bitbucket.org/carlostrub/bapu
go: github.com/davecgh/go-spew@v1.1.1: Get "https://proxy.golang.org/github.com/davecgh/go-spew/@v/v1.1.1.mod": dial tcp xxx.xxx.xxx.xxx:443: connect: can't assign requested address

which is the behavior we expect from the package building machines.

Note: this package has not yet been attempted on armv6/armv7/powerpc64,
so it is unknown how it will fare on them.

Approved by: portmgr (tier-2 blanket)