libgo: delay applying profile stack-frame skip until fixup

libgo: delay applying profile stack-frame skip until fixup

    When the runtime collects a stack trace to associate it with some
    profiling event (mem alloc, mutex, etc) there is a skip count passed
    to runtime.Callers (or equivalent) to skip some known count of frames
    in order to get to the "interesting" frame corresponding to the
    profile event. Now that the profiling mechanism uses lazy fixup (when
    removing compiler artifacts like thunks, morestack calls etc), we also
    need to move the frame skipping logic after the fixup, so as to insure
    that the skip count isn't thrown off by these artifacts.

    Fixes golang/go#32290.

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/179740

From-SVN: r271892