Advent of Code 2015 in Zig

Usage:

1. Use init_day.sh to init solution directory in src/
2. Put your task input to src/dayXX/input.txt
3. Write your code solutions in src/dayXX/main.zig
4. Build and run (see Build and run)

Build and run:

• To build all days run zig build --summary all
  Arg run can be added, to also run all compiled solutions
• To build and run single day use zig build -Dday=<day_number> run

TODO:

• init_day.sh script to create default day dir layout
• init_day.sh change all path to be relative to script, not cwd
• build.zig that iterates over all day dirs, compiles and runs solutions
• build option -Dday=<daynum> to compile and run single day
• day1 solution
• what is the best way to read an input? (I choose @embedFile)
• build option -Dexample=<examplenum> that shows that we need to use example input with some number instead of main input
• build option -Dseq to run solutions sequentially (1,2,3...)