Generate soundbank in NITROFATDIR when it is used

[AntonioND]

Right now the soundbank is always saved in the build directory, but the Makefile should detect if NITROFATDIR is used and place the soundbank there instead.

[AntonioND]

This is the first part of the work: fef7a59

[AntonioND]

It isn't possible to implement this in the build system of the ARM7+ARM9 combined template, so I'm closing this issue.

The soundbank needs to be built before the ARM9 is built so that the soundbank header can be included by ARM9 source code files. This means that the ARM9 should have the soundbank generation rule.

However, the global makefile also needs to have the rule because the final NDS file depends on the soundbank (it is included in the nitroFS filesystem).

devkitARM makefiles don't support this scenario either (for the same reasons I've just mentioned).

I've created https://github.com/AntonioND/architectds to support this kind of situations.