tup: add src as include directory

Improve build script internals

Attempt to add tup support ...

tup is current at 0.7.9 which is riddled with these issues:
- while the examples are good, no ref doc
- headaches using over a vboxsf mount
- headaches at link time
- lack of good platform-depandant variables (e.g. output extension)

So the current sane solution is to continue with the build scripts