Fix another atexit test failure.  (#2247481)
    Fix atexit test failure.
    Notes: Add support for string format notes.
    GCC Plugin: Record settings of -Wstrict-flex-arrays and -fstrict-flex-arrays
    Annobin: Add future test of these options.
    GCC Plugin: Record settings of -Wimplicit-int and -Wimplicit-function-declaration.
    Annobin: Add test for these warnings.
    LLVM Plugin: Fix building with LLVM version 17.
    GCC Plugin: Enable string note format by default.