fix(tools/CROSSTOOL): pass IBEX's CFLAGS
fix(tools/CROSSTOOL): pass IBEX's CFLAGS

Both of GCC and Clang do not support FENV_ACCESS yet. At least GCC has
an option frounding-math which disable certain transformations and
optimization.

Clang is even worse that it does not evn provide an equivalent option
yet.

See: https://bugs.llvm.org/show_bug.cgi?id=8100
See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678#c31

dreal/dreal4,dreal/dreal4,soonho-tri/dreal4,soonho-tri/dreal4,dreal/dreal4,soonho-tri/dreal4,dreal/dreal4,soonho-tri/dreal4