gexec/build.go
func Build(packagePath string, args ...string) (compiledPath string, err error) {
	return doBuild(build.Default.GOPATH, packagePath, nil, args...)
}
func Build(packagePath string, args ...string) (compiledPath string, err error) {
	return doBuild(build.Default.GOPATH, packagePath, nil, args...)
}
/*
Build uses go build to compile the package at packagePath.  The resulting binary is saved off in a temporary directory.
A path pointing to this binary is returned.

Build uses the $GOPATH set in your environment. If $GOPATH is not set and you are using Go 1.8+,
it will use the default GOPATH instead.  It passes the variadic args on to `go build`.
*/