Sets the CFLAGS passed to the C-compiler. Remember to add -fPIC if
you are on a 64-bit platform. If you want to see the defaults
before you modify this variable, check the output of getCFlags().
${SIM_OR_DYNLOAD_OPT_LEVEL} can be used to get a default lower
optimization level for dynamically loaded functions. And
${MODELICAUSERCFLAGS} is nice to add so you can easily modify the
CFLAGS later by using an environment variable.