[PATCH 5/5] gitignore: Ignore golang package directory

[Nick Rosbrook <rosbrookn@gmail.com>]

> With golang, you don’t really distribute package binaries; you only distribute source files.
> 
> However, we don’t want to wait until someone tries to clone the package to see if we’ve broken the build; so the current makefile does a “build test” of the package files.
> 
> Before golang’s “modules” feature, the only way to do this was to have the code to build inside $GOPATH/src/$PACKAGENAME.  We can set GOPATH but we can’t change the “src” component of that.  So we used to set GOPATH to $XENROOT/tools/golang, put the files in $XENROOT/tools/golang/src/$PACKAGENAME, and 
> 
> With the “modules” feature, code can be built anywhere; the build at the moment doesn’t require GOPATH.
> 
> If we’re willing to limit ourselves to using versions of golang which support modules by default (1.12+), then we can probably get rid of this bit instead.  (And if we do want to support older versions, we should really add some code in the configure script to determine whether to build with modules or GOPATH.)
> 
> Nick, any opinions?

I can't think of a reason we need to support anything older than go
1.11, so I think it would be fine to get rid of remnants of the GOPATH
build.

-NR