The build directory which is used by distutils depends on the platform
(e.g. build/lib on Fedora 13, build/lib.linux-i686-2.6 on Ubuntu 9.04).
But test-lib.sh expects to find the build in build/lib which can cause
t5800-remote-helpers.sh to fail early.

Override distutils' choice so that the build is always in build/lib.
Signed-off-by: NMichael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>