Use pkg-config to check modules

Use pkg-config to check modules

Instead of use pre-defined path for dependent modules, e.g libdrm,
libdrm_intel, etc. Use pkg-config helper for cmake instead. This makes
it easy to work with developer own built version of those dependences.

Also remove libGL dependence for 'gbe_bin_generator' which is not required.
libutest.so still requires libGL now but might be fixed by checking real
GL dependence.

v2: Fix build with mesa source (92e6260) and link required EGL lib with utests too.

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Reviewed-by：Zhigang Gong <zhigang.gong@linux.intel.com>