When PKGEXT='.pkg.tar.xz' is set, pacbuilder will not install built packages

What steps will reproduce the problem?
1. Set PKGEXT to '.pkg.tar.xz' in /etc/makepkg.conf
2. Install anything
3. makepkg fails according to pacbuilder, when in reality it works 
perfectly, pacbuilder just can't find the package

What is the expected output? What do you see instead?
The package is expected to install correctly, but instead spits out a 
makepkg failed error.

What version of the product are you using? On what operating system?
Pacbuilder r135 from AUR on Arch Linux x86_64

Original issue reported on code.google.com by MetroidC...@gmail.com on 10 Mar 2010 at 7:02

arfoll / pacbuilder

When PKGEXT='.pkg.tar.xz' is set, pacbuilder will not install built packages #18