Fixing iOS build

Configuring with cmake-ios toolchain fails with error:

    CUDA_TOOLKIT_ROOT_DIR not found or specified
    CMake Error at /usr/local/Cellar/cmake/3.0.2/share/cmake/Modules/FindCUDA.cmake:605 (if):
      if given arguments:

         "CUDA_VERSION" "VERSION_GREATER" "5.0" "AND" "CMAKE_CROSSCOMPILING" "AND" "MATCHES" "arm" "AND" "EXISTS" "CUDA_TOOLKIT_ROOT_DIR-NOTFOUND/targets/armv7-linux-gnueabihf"

       Unknown arguments specified
     Call Stack (most recent call first):
       CMakeLists.txt:334 (find_package)


    -- Configuring incomplete, errors occurred!

Configuring with cmake-ios toolchian and -DNO_CUDA=1 fails with error:

    CMake Error at opensubdiv/CMakeLists.txt:80 (include_directories):
      include_directories given empty-string as include directory.

because of empty OPENGLES_INCLUDE_DIR for iOS