bug#26941: New font-build-system

[Arun Isaac <arunisaac@systemreboot.net>]

>>>> A side issue: I feel that the `install-file' procedure should print out
>>>> what it's doing to stdout (or some log port). Something like:
>>>>
>>>> (format #t "~a -> ~a~%" source destination)
>>>>
>>>> This would save us the trouble of implementing this log printing
>>>> everywhere `install-file' is called. For example, this could be very
>>>> useful in the 'install' phase of the font-build-sytem. WDYT?
>>>
>>> Do we really need to print something in the first place?  :-)  Some
>>> procedures in (guix build utils) do that, indeed, but I’m not sure it’s
>>> useful for something as simple as ‘install-file’.  Thoughts?
>>
>> Yes, I think it is really important. Without the verbose output, one
>> will have to stare at a blank screen, guessing at what is
>> happening. Long verbose output feels reassuring that something is going
>> on. :-) Also, verbose output for `install-file' might help in debugging
>> correct source/destination paths.
>
> OK.  I’m not entirely convinced, because I think that either the build
> completes and it’s easy to check that the files are where you wanted
> them to be, or it fails, and you get an exception.  I’m not strongly
> opposed either, so perhaps something to consider in the next
> ‘core-updates’ cycle.

Should I send a patch for this?

>> From a0bda2fc48c6d2c7809805251154c49e8be76d67 Mon Sep 17 00:00:00 2001
>> From: Arun Isaac <arunisaac@systemreboot.net>
>> Date: Mon, 15 May 2017 20:08:57 +0530
>> Subject: [PATCH 1/5] build-system: Add 'font-build-system'.
>>
>> * Makefile.am (MODULES): Add 'guix/build-system/font.scm' and
>>   'guix/build/font-build-system.scm'.
>> * guix/build-system/font.scm: New file.
>> * guix/build/font-build-system.scm: New file.
>> * doc/guix.texi (Build Systems): Add 'font-build-system'.
>
> Alright, OK for this and the following patches.

I'll push these shortly, and begin work on migrating the other font
packages to the new font-build-system.