Fixed installer's Makefile to properly create a cross-compiled executable

[Zedjones]

Currently, all files in loader/ are compiled using the CROSS specified tool-chain, but the end installer executable gets compiled using the compiler set in the CC environment variable.

This change fixes that, using the CROSS tool-chain for the final output as well.

[andreiw]

This is an interesting perspective. I specifically wanted a "native" installer so that you could create a bootable media not on a PPC/Linux system. Basically, if you want a PPC installer you should native build.

I'll manually merge this... instead of CROSS there will be ICROSS (i.e installer cross)