Added cross-compile flags for 32bit Linux

Specified the -m32 GCC flag when using `mode=release32` in SCons.
This will compile a 32bit version of the program so that now I don't
have to boot a 32bit VM everytime! yay!
Tests now return 1 if they failed

This way tools like Make know if the `tesstest` program failed.
Dist Makefile tests the build and uses cross-comp

Automated rules to test the build for distribution and abort if the
tests fail. Also uses cross-compilation to make the 32bit distribution
package.