m_fixed: asm: cc is not a register

gcc accepts

  __asm__ ( "" : : : "%cc");

but not clang:

    error: unknown register name '%cc' in asm
        :"%cc", "%edx"         // edx and condition codes clobbered

'cc' is not a register, thus '%cc' is rightfully not accepted.

Repro: build the project on x86_64 with:
    cmake -H. -Bbuild -DCMAKE_C_COMPILER=clang -DCMAKE_SIZEOF_VOID_P=4 -DCMAKE_C_FLAGS="-m32"