add example pure C project

[mcandre]

Need to find a suitable pure C alternative to the portable filesystem library.

[mcandre]

Maybe libuv

https://conan.io/center/libuv

http://docs.libuv.org/en/v1.x/fs.html

Unfortunately, any third party dependency makes task runners more difficult to write. We would have to find a way to integrate the additional include and linker directories into the rez.{c,cpp} compilation command.

[mcandre]

Good news, basic filesystem things are accessible via some (hidden and disabled by default) POSIX functions. A few manual wrapper utility functions are necessary to provide practically high level semantics for these operations.

Instead of C++ std::map, we can use a slower, linear associative array by scanning through all the elements in an array of keys (strcmp) and using the corresponding index (if any) to get the value from an array of values. That's not scalable, but most projects don't define more than a few dozen build tasks.

Tracking a small C example in branch "issue-31".

• [x] Test on macOS
• [x] Test on native Linux (Ubuntu)
• [x] Test on WSL

[mcandre]

Yuck, MSVC C (non C++) options are limited in COMSPEC Windows.

https://docs.microsoft.com/en-us/windows/win32/fileio/file-systems

https://stackoverflow.com/questions/4180351/unable-to-delete-a-folder-with-shfileoperation/4180426

TODO:

• [x] Test on COMSPEC Windows