Remove gcc, gcc-c++ and make from minimal build root

[Gerd Hoffmann]

  Hi,

> I don't think the original question was all that great.  If we were to
> script the change to add the BRs, it would take time but it would
> mostly be a one-time cost.  Reducing buildroot time creation, network
> bandwidth, and storage savings is a reduction over each new buildroot
> instance creation over a long period of time.

IMO it isn't that clear there is a significant win due to the caching
mock is doing.  mock creates the minimal buildroot every once in a
while, then keeps reusing it for builds.  So, with a hot cache the build
goes like this:

  (1) unpack cached minimal buildroot
  (2) rpm install build deps
  (3) do the build

Taking gcc out of the minimal buildroot is an obvious win for packages
not using gcc.  But for packages using gcc it just moves gcc
installation from step (1) to step (2), and I expect this will slow down
the builds due to unpacking the cached buildroot being faster than doing
an rpm install.

So effectively we are going to trade faster non-gcc builds for slower
gcc builds.  Which still might be a net win at the end, but just from
looking at the proposal it isn't obvious whenever it actually is or not.

cheers,
  Gerd