libimobiledevice fails to cross build from source for armhf, because its
check for a consistent Python development environment fails there. It is
unclear to me why this succeeds for other architectures. Generally, one
can see that all cross builds try to use the build architecture library
directory. The typical root cause is using the wrong sysconfigdata and
the usual solution is to export _PYTHON_SYSCONFIGDATA_NAME. I'm
attaching a patch for your convenience. Please consider applying it.

Helmut