Enable JFR in our builds, ahead of upstream default.
    
    Only enable JFR for JIT builds, as it is not supported with Zero.
    Turn off JFR on x86 for now due to assert(SerializePageShiftCount == count) crash.
    Explicitly list jfr.jar, default.jfc & profile.jfc in the spec file.
    Introduce jfr_arches for architectures which support JFR.
    Use sa_arches for libsaproc.so inclusion.
    Move LTO handling to same location as other compiler flags handling.