Rusticl: Rework the compilation pipeline a little and also allow to dump compilation logs directly to stderr
While at it I also add validation for the SPIR-V and other things.. anyway...
$ RUSTICL_DEBUG=program RUSTICL_ENABLE=swrast:0 ./minimal-spirv-runner --platform rusticl --device llvmpipe module.spv test
selected platform 'rusticl' and device 'llvmpipe (LLVM 15.0.7, 256 bits)'
(file=input,line=0,column=0,index=8): ID 3[%3] has not been defined
%1 = OpFunction %void None %3
minimal_spirv_runner.c:173: error: opencl returned -11
Closes: #8771 (closed)