GNU and POSIX core utils rewritten in zig.

This is just a playground for me to use zig a bit more.

References:

• https://en.wikipedia.org/wiki/List_of_POSIX_commands
• https://en.wikipedia.org/wiki/List_of_GNU_Core_Utilities_commands

To add a new program, create program_name.zig in src/ and add program_name to the programs array in build.zig.

LICENSE: GPLv3