cmake: Add an Android platform and toolchain

Signed-off-by: Adrian Marius Negreanu <adrian.m.negreanu@intel.com>
cmake,util: Add Android Waffle support

Signed-off-by: Adrian Marius Negreanu <adrian.m.negreanu@intel.com>
cmake: Add FindWaffle.cmake

Piglit searches waffle by using pkg_check_modules.
If one tried to use the android toolchain along cmake,
waffle won't be found, since pkg_check_modules relies on
pkg-config(missing on android)

To fix this, add a "cmake find-module" for Waffle.

Signed-off-by: Adrian Marius Negreanu <adrian.m.negreanu@intel.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
cmake: Use find_package to find Waffle

replace pkg_check_modules with find_package

Signed-off-by: Adrian Negreanu <groleo@gmail.com>
doc: Add build instructions for Android

Signed-off-by: Adrian Marius Negreanu <adrian.m.negreanu@intel.com>
cmake: fix for missing opengl headers

when the client library provides only gles2 headers,
some references to OPENGL_INCLUDE_PATH will become undefined

Signed-off-by: Adrian Marius Negreanu <adrian.m.negreanu@intel.com>