[error] Found no matching devices! Quitting! when running Optiminer, Believe it is an OpenCL issue

When I execute the command
./optiminer-zcash -s eu1-zcash.flypool.org:3333 -u t1Yszagk1jBjdyPfs2GxXx1GWcfn6fdTuFJ.example -p password
I get

[2018-01-10 16:43:31.192] [info] Optiminer/Zcash 1.7.0 © Optiminer 2017
[2018-01-10 16:43:31.192] [info] Connecting to eu1-zcash.flypool.org:3333.
[2018-01-10 16:43:31.267] [error] Found no matching devices! Quitting!

as the response. I believe it is an issue with my OpenCL. I am running a Radeon HD 6870 with opensource Radeon Driver on Ubuntu 17.04. When I run clinfo, the noteworthy thing I notice is

clCreateContextFromType(NULL, CL_DEVICE_TYPE_ACCELERATOR) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_CUSTOM) No devices found in platform
clCreateContextFromType(NULL, CL_DEVICE_TYPE_ALL) Success (1)

What should I do to remedy this?