Here are my notes on the installation. I think I might be missing a step or two so if you follow these and run into issues, please post a comment!!!
These instructions should also mostly work in 32 bit Linux distros, but you won't need to install as much (remove the packages with "i386", or "32" in their names).
Step 1: Prep Ubuntu for 32 bit compilation
sudo apt-get install build-essential lib32z1-dev g++-multilib gcc-multilib ia32-libs libssl1.0.0 libssl1.0.0:i386 libjpeg8 libjpeg8:i386
Next, get and install libpng14 from source:
tar xvf libpng-1.4.8* cd libpng-* ./configure CFLAGS=-m32 --prefix=/ make check sudo make install
32 bit distros should remove "CFLAGS=-m32" and just use this line instead:
[Troubleshooting] If you get the error: "configure: error: C compiler cannot create executables" check the config.log file. If the problem is: "/usr/bin/ld: cannot find crt1.o: No such file or directory" then you did not install g++-multilib gcc-multilib.
If you get: "configure: error: zlib not installed" you did not install lib32z1-dev
Now install Eagle:
chmod a+x eagle-lin*
Good Luck and keep building OSHW!!!