Moving general useful procedures to the utils-modules

[swedebugia]

Hi

I found this in guix/build/cargo-build-system.scm:

(define (touch file-name)
  (call-with-output-file file-name (const #t)))

I think we should move useful ones like this to (build utils) and 
consider merging (build utils) and (import utils) into a single 
utils-module.

I think we should also consider factoring out some of these utils in a 
separate guix-utils library that can be used by other guile-projects 
WITHOUT depending on the whole of guix.

These steps makes it easier for newcomers to overview our many modules 
and use our very valuable tools.

--
Cheers Swedebugia