Build fix

libGL was broken (probably by the recent namespace change, not sure)

Change-Id: I27e461f82a652cb8f9a646ab1d4091195efc454b
Reviewed-on: https://swiftshader-review.googlesource.com/5054
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>