smooth fails to cross build from source, because it builds for the build
architecture. debhelper sees a configure script and expects it to set up
compilers, but this configure script does not configure anything. It can
be fully ignored. A first step is overriding the detected builsystem to
makefile. At that point, dh_auto_build will pass cross tools to make,
which is what this build system needs. A secondary problem is that it
hard codes the build architecture pkg-config all over the place. Once
making it substitutable, smooth can be cross built. Please consider
applying the attached patch and also forward the contained cross.patch
upstream as it is beneficial to other distributions.

Helmut