Build fail on MacOS
I'm trying to build xmrig-amd on my iMac with Radeon Pro 580 but it fails on the make.

Can I do something to fix it?

Terminal output cmake:

```
cmake ..
-- The C compiler identification is AppleClang 9.1.0.9020039
-- The CXX compiler identification is AppleClang 9.1.0.9020039
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found UV: /usr/local/lib/libuv.a  
-- Looking for syslog.h
-- Looking for syslog.h - found
-- Found MHD: /usr/local/lib/libmicrohttpd.dylib  
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/me/Desktop/xmrig-amd-master/build

```
Terminal output make:
```
make
Scanning dependencies of target xmrig-amd
[  2%] Building CXX object CMakeFiles/xmrig-amd.dir/src/amd/OclCache.cpp.o
In file included from /Users/me/Desktop/xmrig-amd-master/src/amd/OclCache.cpp:30:
In file included from /Users/me/Desktop/xmrig-amd-master/src/amd/OclCache.h:28:
In file included from /Users/me/Desktop/xmrig-amd-master/src/amd/GpuContext.h:28:
/Users/me/Desktop/xmrig-amd-master/src/3rdparty/CL/cl.h:33:10: fatal error: 'OpenCL/cl_version.h' file not found
#include <OpenCL/cl_version.h>
         ^~~~~~~~~~~~~~~~~~~~~
1 error generated.
make[2]: *** [CMakeFiles/xmrig-amd.dir/src/amd/OclCache.cpp.o] Error 1
make[1]: *** [CMakeFiles/xmrig-amd.dir/all] Error 2
make: *** [all] Error 2

```