The program source files memory footprint is reduced (-30%) by eliminating
comments in the generated kernel headers.  Hash calculation of each source
file  is performed at compile time and incrementally extended at runtime
with the options & tInstance vectors.  Overall performance increased up to
21%, up to the point that the GPU becomes the bottleneck, and the overhead
to launch the same (small) kernel was improved by 63%.

#3043)
* Reduced overhead of kernel caching for OpenCL & CUDA.
The program source files memory footprint is reduced (-30%) by eliminating
comments in the generated kernel headers.  Hash calculation of each source
file  is performed at compile time and incrementally extended at runtime
with the options & tInstance vectors.  Overall performance increased up to
21%, up to the point that the GPU becomes the bottleneck, and the overhead
to launch the same (small) kernel was improved by 63%.
* Fix couple of minor cmake changes
* Move spdlog fetch to use it in bin2cpp link command
Co-authored-by: pradeep <pradeep@arrayfire.com>
(cherry picked from commit  3cde757 )