[external][libm] add -Wno-maybe-uninitialized
[external][libm] add -Wno-maybe-uninitialized

Some older code triggers this warning on gcc 12.1.

hollanderic/lkstuff,littlekernel/lk,hollanderic/lkstuff,hollanderic/lkstuff,littlekernel/lk,littlekernel/lk,littlekernel/lk,hollanderic/lkstuff