OpenWrt

1. Install XCode & Macports

# sudo port install coreutils asciidoc bzip2 fastjar flex getopt gtk2 intltool
python26 rsync ruby sdcc unzip gettext libxslt bison gawk autoconf wget gmake ncurses e2fsprogs ossp-uuid gawk findutils
gnutar bzr binutils jikes zlib openssl p5-extutils-makemaker util-linux libutil-linux e2fsprogs osso-uuid

2. Using Disk Utility to create a sparse disk image with case sensitive (Format: Mac OS Extended (case-sensitive) ). Mount it by double click

3. Check out the source code

4. Modify makefile

I have built a customized version of OpenWrt. It's used for my RT-N16 wireless router.
 
It can be downloaded from here:
https://www.jianyu.net/openwrt/
 
 
The build is based on the patches from George Kashperko, with a few modifications: