Minor edits to configurations' make_defs.mk files.

Details:
- Redefined CFLAGS, CFLAGS_NOOPT, and CFLAGS_KERNELS so that CFLAGS_NOOPT
  is defined first and then the other two are defined in terms of
  CFLAGS_NOOPT. This textually cleans up the definitions and makes them a
  little easier to read.