experiment: allow nimony compile projects outside compiler folder

[mrgaturus]

• remove hardcoded nifcache path prefixes
• make nimony be able compile projects outside compiler folder
• allow locate a custom nifcache path using a --nifcache:PATH command line argument (nimony only)
• makefiles, nif files, and c files have paths relative to nifcache folder (ideal for tests)

this is an experiment so i don't think this would be a proper solution right now, at least this experiment could be useful to a proper implementation of this in a future.

[Araq]

Bring this over the finish line please.

[mrgaturus]

updated to the latest commit.
i made it be relative to nifcache using setCurrrentDir(<nifcache path>) in nimony main command because that is how meson generate ninja stuff, a common pattern of a meson project is:

meson build
cd build
ninja

and all paths inside build.ninja are relative to the build folder
i don't know if you want this behavior so that's why this is an experiment for now

[Araq]

i don't know if you want this behavior so that's why this is an experiment for now

I usually go into the opposite direction, see how for example nim c -r tools/gen_tags simply works, but not if you cd'ed to tools/ first.

[mrgaturus]

in this experiment you don't need cd to nifcache first, your example works as well. i mean the fact all paths inside nifcache files are relative to the nifcache path, so running for example nimony c tests/nimony/ffi/theader.nim you will see ../tests/nimony/ffi/theader.nim in the nifcache files instead tests/nimony/ffi/theader.nim