[Bug other/114191] Flags "Warning" and "Target" don't mix well in target.opt files

[gjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114191

--- Comment #2 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> Wmisspelled-isr
> Target C C++ Var(avr_warn_misspelled_isr) Init(1)
> Warn if the ISR is misspelled, ...
> 
> should eventually work?

With that, the warnings appear as they should, but the option is not
recognized:

$ avr-gcc signal.c -S -Wmisspelled-isr
error: unrecognized command-line option '-Wmisspelled-isr'

$ avr-gcc signal.c -S -Wno-misspelled-isr
error: unrecognized command-line option '-Wno-misspelled-isr'

$ avr-gcc signal.c -S -Werror=misspelled-isr
error: '-Werror=misspelled-isr': '-Wmisspelled-isr' is not an option that
controls warnings