Enhances the release script to check that the specified tag
is also the tag that is currently checked out. In addition to that, the
script also ensures that the tag and the version specified in version.go
match.
These result in an error with the current release script as is. Those
that want to run `lnd` on their iPhone/iPad can instead use the
`gomobile` bindings.
Notably, solaris/amd64 and illumos/amd64 were added in go1.13. The
others were have been supported previously but were not build targets.
After go1.13, nacl/* will no longer be supported and plan9/* is still
considered experiemental. As a result they are omitted.
In this commit, we create a new `build/release` package which houses the
build instructions and scripts that we need to do deterministic builds
across Windows, Linux, and MacOS.
With this new system, it's now possible for all `lnd` developers, as
well as users to verify the posted build binaries. This wasn't possible
in prior release as only in Go 1.13 did deterministic builds becomes
easier/possible. See the new `README.md` for further details.
