cmd/go: test that Go binaries can be run on QEMU in user-mode

We have a workaround in place in the runtime (see CL 16853 and
CL 111176) to keep arm and arm64 Go binaries working under QEMU
in user-emulation mode (Issue #13024).

This change adds a regression test about arm/arm64 QEMU emulation
to cmd/go.

Change-Id: Ic67f476e7c30a7d7852d9b01834f1dcabfac2ff7
Reviewed-on: https://go-review.googlesource.com/111477


Reviewed-by: Ian Lance Taylor <iant@golang.org>