Compilation fails in Ubuntu 21.10 presumably due to clang version behavior change

[JMPZ11]

Describe the bug

When attempting to compile using "scons -j$(nproc)" in Ubuntu 21.10 the warning "error: variable '...' set but not used [-Werror,-Wunused-but-set-variable]" is encountered in many places throughout the code (the first few are in cereal).

Workarounds are described here: https://gcc.gnu.org/gcc-4.6/porting_to.html

I am not familiar enough with the code to "fix" the underlying issue.
Applying the annotation __attribute__((__unused__)) to the instances does resolve the error, but requires changes across multiple repos (may be unavoidable...)

A "quick" workaround is to add the following to the root SConstruct file around line 192 (CCFLAGS list)

"-Wno-error=unused-but-set-variable",

This however leads to more errors - still diagnosing...

OS Version

Ubuntu 21.10

openpilot version or commit

f1c77f9

Additional info

No response

[JMPZ11]

@pd0wm The commit was reverted - could you reopen the issue?

@adeebshihadeh Guessing #22952 had unintended consequences - would making the changes conditional help? Different approach? Let me know if I can help.