Error on compiling time for AMD GPU (macOS)
I downloaded and compiled `xmrig-amd` from [releases](https://github.com/xmrig/xmrig-amd/releases) with no issue. But when I start `xmrig` with default config I get the following output:

```
 * ABOUT        XMRig-AMD/2.14.6 clang/11.0.0
 * LIBS         libuv/1.31.0 OpenCL/1.2 OpenSSL/1.0.2t microhttpd/0.9.63 
 * CPU          Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz x64 AES
 * ALGO         cryptonight, donate=5%
 * POOL #1      donate.v2.xmrig.com:3333 variant auto
 * COMMANDS     hashrate, pause, resume
[2019-11-20 11:19:20] compiling code and initializing GPUs. This will take a while...
[2019-11-20 11:19:20] found OpenCL GPU: Intel(R) UHD Graphics 630, cu: 24
[2019-11-20 11:19:20] found OpenCL GPU: AMD Radeon Pro 555X Compute Engine, cu: 12
[2019-11-20 11:19:20] #00, GPU #01 AMD Radeon Pro 555X Compute Engine, i:192 (8/256), si:2/2, u:8, cu:12
[2019-11-20 11:19:20]              0.38/1.00/4 GB
[2019-11-20 11:19:20] GPU #1 compiling...
[2019-11-20 11:19:33] Error CL_BUILD_PROGRAM_FAILURE when calling clBuildProgram.
Build log:
Error returned by cvms_element_build_from_source
[2019-11-20 11:19:33] Failed to start threads.
```

### My hardware: 
- MacBook Pro 2019 15"
- AMD Radeon Pro 555X

I don't understand what this error means.