Auto merge of #106619 - agausmann:avr-object-file, r=nagisa

Fix unset e_flags in ELF files generated for AVR targets

Closes #106576

~~Sort-of blocked by gimli-rs/object#500~~ (merged)

I'm not sure whether the list of AVR CPU names is okay here. Maybe it could be moved out-of-line to improve the readability of the function.