Error libGL.so: cannot open shared object file using Android emulator

This works for me on Ubuntu 14.04 64-bit:

$ sudo apt-get install libgl1-mesa-dri
$ sudo ln -sv /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1 /usr/lib/x86_64-linux-gnu/libGL.so

As I'm using 64-bit Ubuntu 12.04. So, I did this

$ sudo apt-get install git-core gnupg flex bison gperf build-essential \
  zip curl libc6-dev libncurses5-dev:i386 x11proto-core-dev \
  libx11-dev:i386 libreadline6-dev:i386 libgl1-mesa-glx:i386 \
  libgl1-mesa-dev g++-multilib mingw32 openjdk-6-jdk tofrodos \
  python-markdown libxml2-utils xsltproc zlib1g-dev:i386
$ sudo ln -s /usr/lib/i386-linux-gnu/mesa/libGL.so.1 /usr/lib/i386-linux-gnu/libGL.so

On Fedora

sudo yum install mesa-libGL-devel

http://learnedstuffs.wordpress.com/2012/07/17/fixing-ubuntu-error-failed-to-load-libgl-so/

apt-get install libgl1-mesa-dev

worked for me