Add makepkg for archlinux package generation

I tend to use my Mac to create or update archlinux packages.   Like `dpkg` the program won't allow you to install any packages.

```
The following options won't work:

-i, --install    Install package after successful build
-r, --rmdeps     Remove installed dependencies after a successful build
-s, --syncdeps   Install missing dependencies with pacman
--asdeps         Install packages as non-explicitly installed

Maybe others I haven't tested all the options

NOTE: I usually don't use this function but if you want to create a binary package, make sure to pass the -d option.
```
Can a test be added to do something more substantial then e.g. `--version` or `--help`? See `cmake.rb` for an example of a formula with a good test. Thanks!