Allow specifying dependencies in `.compile.` to make rebuild logic correct

[arnetheduck]

Summary

When compiling a c file, it might have dependencies (its #include files) which nim doesn't know about - when such dependencies are changed, the C file needs recompilation which currently does not happen.

Description

This could be resolved by adding a parameter to .compile("myfile.c", flags = "...", dependencies = [myfile1.h, ...]). - alternatively, a smarter version would discover such dependencies automatically (using gcc -MD and similar flags, parsing the output)

Alternatives

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Examples

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Backwards Compatibility

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Links

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[Araq]

Fwiw, it was always supposed to be used as "if .c file deps changed, invoke with the -f switch".

[arnetheduck]

-f is a blunt tool - ie projects might have hundreds of c files to compile (like ours do) so recompiling all of them is messy - it's also inconvenient when using any sort of tooling (like a code editor) where adding a flag to a one-off compilation requires extra manual steps.

The aim is to have nim c "just work" without having to teach magic flags like -f which are only used in exceptional cases.