Fix the use of -fno-approx-func along with -Ofast or -ffast-math

Fix how -fapprox-func interact correctly with the other floating point options.
Reported bug Number 52565: https://bugs.llvm.org/show_bug.cgi?id=52565

Differential: https://reviews.llvm.org/D114564
Reviewer: @andrew.w.kaylor