configure.ac: add missing LLVM components for OpenCL

Coverage and LTO seems to be hard requirements for Clang, while
coroutines is needed as of LLVM/Clang 4.0.

Mark the last one as "optional" so we handle every case.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Tobias Droste <tdroste@gmx.de>
1 file changed