We need to be able to read in and parse files using the ClangIR dialect
in order to test this part of the functionality.
This change adds the minimum cir-opt tool needed to read and parse cir
files and write them back to text. This tool will later be extended to
add features for lowering from CIR to other MLIR dialects and to run CIR
passes as they are upstreamed.
607a1f2ace