Ability to specify compiler package for Go build system.

[Hilton Chain]

Hi Guix,

I'm trying to package wakatime-cli[1], while Guix uses Go 1.17 as the default, 
the package requires
Go 1.19 at the current version (v1.60.4).

Though it's possible to package the last version supports Go 1.17 (v1.38.0), I 
wonder if we can
adjust the build system so that a Go package could be specified via an argument 
in the package
definition.

Thanks!

[1] <https://github.com/wakatime/wakatime-cli>