[Docker-maint] Bug#799907: golang 1.5 does not build under arm64

[Potter, Tim (Converged Cloud)]

Package: golang
Severity: important
Version: 2:1.5-1~exp1
Tags: patch

Hi there.  I’ve found and fixed a build bug on arm64 for golang in the delian-experimental branch, 
fixed by the attached patch.  According to the GoArm page on the golang wiki [1] GOARCH needs
to be set to arm64.

The patch also includes a fix for the “unrecognised build host instruction set”
error, where the error message displays $BUILD_HOST_ARCH_CPU when the variable being
checked is DEB_BUILD_ARCH_CPU which I think it not what’s intended.


Regards,

Tim.

[1] https://github.com/golang/go/wiki/GoArm