Use a variable in the Makefile to set the GO_VERSION for the builds.
GO_VERSION is defaulted in all Makefiles as `1.10.2`, but can be set when running make: `make GO_VERSION=1.10.1 deb`.
Signed-off-by: corbin-coleman <corbin.coleman@docker.com>
Upstream-commit: 0fe741746287335a5ba4afaf06be301915324e5a
Component: packaging