Hi, it's not a problem in compiling, it's a problem in linking. WriteLog() is declared in files.h but not implemented anywhere.
Perhaps change lines 59 and 60 of files.h from:
void WriteLog(const char *text);
void WriteLogDouble(const char *text, double value);
to
#define WriteLog(text) if(0)
#define WriteLogDouble(text,value) if(0)
This should make it compile, though there won't be any logging. A better fix would be to make them do something useful.
I don't even get that far: I get errors like this:
/usr/include/CL/cl.hpp: In function ‘cl_int cl::UnloadCompiler()’:
/usr/include/CL/cl.hpp:1606:12: error: ‘::clUnloadCompiler’ has not been declared
/usr/include/CL/cl.hpp: In constructor ‘cl::Image2D::Image2D(const cl::Context&, cl_mem_flags, cl::ImageFormat, size_t, size_t, size_t, void*, cl_int*)’:
/usr/include/CL/cl.hpp:2365:19: error: ‘::clCreateImage2D’ has not been declared
/usr/include/CL/cl.hpp: In constructor ‘cl::Image2DGL::Image2DGL(const cl::Context&, cl_mem_flags, GLenum, GLint, GLuint, cl_int*)’:
/usr/include/CL/cl.hpp:2410:19: error: ‘::clCreateFromGLTexture2D’ has not been declared
/usr/include/CL/cl.hpp: In constructor ‘cl::Image3D::Image3D(const cl::Context&, cl_mem_flags, cl::ImageFormat, size_t, size_t, size_t, size_t, size_t, void*, cl_int*)’:
/usr/include/CL/cl.hpp:2464:19: error: ‘::clCreateImage3D’ has not been declared
/usr/include/CL/cl.hpp: In constructor ‘cl::Image3DGL::Image3DGL(const cl::Context&, cl_mem_flags, GLenum, GLint, GLuint, cl_int*)’:
/usr/include/CL/cl.hpp:2510:19: error: ‘::clCreateFromGLTexture3D’ has not been declared
/usr/include/CL/cl.hpp: In member function ‘cl_int cl::CommandQueue::enqueueMarker(cl::Event*) const’:
/usr/include/CL/cl.hpp:3745:13: error: ‘::clEnqueueMarker’ has not been declared
/usr/include/CL/cl.hpp: In member function ‘cl_int cl::CommandQueue::enqueueWaitForEvents(const std::vector<cl::Event>&) const’:
/usr/include/CL/cl.hpp:3752:13: error: ‘::clEnqueueWaitForEvents’ has not been declared
/usr/include/CL/cl.hpp: In member function ‘cl_int cl::CommandQueue::enqueueBarrier() const’:
/usr/include/CL/cl.hpp:3867:13: error: ‘::clEnqueueBarrier’ has not been declared
which means my installed OpenCL implementation must be kinda hosed (those errors are internal to CL/cl.hpp and probably nothing to do with mandelbulber).