BUILD: Enable CPU optimizations by default.
BUILD: Enable CPU optimizations by default.

 Per discussion on the conference call, we enable all machine-specific
optimizations by default. Binary distributions would have to configure
with --disable-optimizations to ensure portability.
 Also, specific optimizations can still be controlled individually.

shssf/ucx,abouteiller/ucx,sergsagal1/ucx_rocm,shssf/ucx,abouteiller/ucx,sergsagal1/ucx_rocm,abouteiller/ucx,sergsagal1/ucx_rocm,abouteiller/ucx,shssf/ucx