Make ARM »Hello World« compile

To implement this, I had to finally tackle the CPU detection issue. Implementation is mostly what I had right before DConf, with a few extra fixes.

EH currently doesn't work at all, even with `-arm-enable-ehabi -arm-enable-ehabi-descriptors`, but I'm pretty sure it did before. Investigating…

The hard/soft float versions are not yet set according to the actual target.