Bug#985357: trackballs FTCBFS: uses the build architecture preprocessor

[Helmut Grohne]

Source: trackballs
Version: 1.3.2-1
Tags: patch upstream
User: debian-cross at lists.debian.org
Usertags: ftcbfs
X-Debbugs-Cc: Nilesh Patra <nilesh at debian.org>

trackballs fails to cross build from source, because it uses the build
architecture preprocessor during guile-snarf invocations. As a
consequence, it fails locating gmp, which is only requested for the host
architecture. The issue is manifested in the CMakeLists.txt, where it
says CPP=cpp. Beyond the issue of what is being passed here, it also
uses an unportable form of environment passing. Please use
${CMAKE_COMMAND} -E env instead. Figuring the right preprocessor is not
entirely trivial. CMake does not seem to know about it by itself. The
closest we can get likely is passing -E to the relevant compiler. I'm
attaching a patch that makes trackballs cross buildable for your
convenience.

Helmut