d/shuffle-binaries: Fix binary shuffling script for cross-building

d/shuffle-binaries: Fix binary shuffling script for cross-building

`ldd` doesn't work with cross-builds, so use `file` to detect scripts
and `strings | grep` for identifying linked libraries.  Even though
debhelper depends on file, make the requirement explicit.

Heavily simplify script inner loop.  While the core of that inner loop
was often executed only once, it is best to shrink inner loops.

Signed-off-by: Elliott Mitchell <ehem+debian@m5p.com>
Acked-by: Hans van Kranenburg <hans@knorrie.org>