Tweak make targets MacOS M1 xc to Linux arches (#10706)
Tweak make targets MacOS M1 xc to Linux arches (#10706)

The cross-build and cross-compile make targets are meant to let you
compile from host architecture (e.g. Mac M1) to target architectures
(e.g. Linux AMD64). They don't currently work for Mac M1 to other
targets.

There are a couple problems:

 - Some syntactical errors in the Makefile targets.
 - Golang doesn't like it when you use GOBIN in cross-architecture
   installs.

This commit makes cross builds work on Mac, while preserving existing
usage (used in a build step of docker/lite/Docker.ubi8.arm64.mysql80):

 - Fixes syntactical errors in conditional statement in make target.
 - Replaces GOBIN usage with VTROOTBIN during build steps, preserving
   GOBIN usage in install steps.

This commit also does some refactoring to use `go build` instead of
`go install` for "build" targets.

Signed-off-by: Max Englander <0706025b2bbcec1ed8d64822f4eccd96314938d0@planetscale.com>
mahak/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,mahak/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,vitessio/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,mahak/vitess