inlining failed in call to 'always_inline': target specific option mismatch

[Georg-Johann Lay]

This error pops up in the testsuite for avr.

As far as I understand, this is due to target-specific optimization like 
in avr-common.cc:

    { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_mgas_isr_prologues, NULL, 1 },
    { OPT_LEVELS_1_PLUS, OPT_mmain_is_OS_task, NULL, 1 },
    // Stick to the "old" placement of the subreg lowering pass.
    { OPT_LEVELS_1_PLUS, OPT_fsplit_wide_types_early, NULL, 1 },

My question is how to fix this.

The backend does not implement can_inline_p, and adding "Optimization" 
to the respective option definition in avr.opt does not help.

Johann