[AVR] Backport #152269 to the 21.x branch

[aykevl]

This is an AVR backend bug (present since LLVM 20, #152097) that is now fixed in main but I would like to see this bug fixed in the coming release as well. It prevents compilation of (at least) compiler-rt with assertions enabled.

/cherry-pick aeeb9b5

[llvmbot]

This is an AVR backend bug (present since LLVM 20, #117558) that is now fixed in main but I would like to see this bug fixed in the coming release as well. It prevents compilation of (at least) compiler-rt with assertions enabled.

/cherry-pick aeeb9b5

Error: Command failed due to missing milestone.

[RKSimon]

/cherry-pick aeeb9b5

[llvmbot]

/pull-request #152682