Are you ISO26262-compliant and your software is ASIL-A or higher? If no, why would you care about MISRA? If yes, how did you qualify a recent GCC?
Safety-critical automotive software development depends on tool qualification, which is often a lot of tedious work. There must be a spec, there must be tests, there must be proof that the tests cover the full spec, you must have a process to inform users about bugs. There is no free compiler which provides this.