[Driver] Default to -fno-math-errno for musl

musl does not set errno in math functions: https://wiki.musl-libc.org/mathematical-library.html, https://git.musl-libc.org/cgit/musl/tree/include/math.h?id=cfdfd5ea3ce14c6abf7fb22a531f3d99518b5a1b#n26.

Reviewed By: srhines, MaskRay

Differential Revision: https://reviews.llvm.org/D116753