Build does not work in build folder

[dchassin]

Problem description

Build process only work in top source folder. It does not work in build folder, for example. It should work from any folder. For the truly OCD developer this is irritating because building in the top folder can create litter in the source tree that we don't like.

Steps to reproduce

% autoreconf -isf
% mkdir build
% cd build
% ../configure
% make system

Expected behavior

The usage shown should result in an install just like doing so in the top source folder does. However, all the build files should be in the build folder and the top source folder should not have any intermediate files created (other than the standard autoconf files).

[dchassin]

Fix is not complete because ../configure cannot find custom.mk.