Run cppcheck on PRs
Run cppcheck on PRs

Add a CI run with cppcheck, a static C++ code analyzer.

googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc