intel/compiler: add ability to override shader's assembly

intel/compiler: add ability to override shader's assembly

When dumping shader's assembly with INTEL_DEBUG=vs,tcs,...
sha1 of the resulting assembly is also printed, having environment
variable INTEL_SHADER_ASM_READ_PATH present driver will try to
load a "%sha1%.bin" file from the path and substitute current
assembly with the one from the file.

Signed-off-by: Danylo Piliaiev <danylo.piliaiev@globallogic.com>
Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>