Fixes and tweaks for makerpo

Hi,

I've created a script to spin up a i686 and x86_64 `arch-chroot` for testing the MATE package builds. I want to streamline the process a little, so here is a little update to `makerpo`.

  * Fixed `makerpo -r`.  
  * `makepkg` will only install packages that are needed.
  * `makepkg` will produce a `build.log` for each package. I found this useful yesterday when talking with the devs on IRC.
  *  `pacman` will no longer seek confirmation if an interactive prompt has already provided consent.

Regards, Martin.