Avoid #include <math.h> in posix_math.cpp
Avoid #include <math.h> in posix_math.cpp

The IOS target breaks the build for some systems.

ronen/Halide,mikeseven/Halide,myrtleTree33/Halide,myrtleTree33/Halide,dan-tull/Halide,jiawen/Halide,aam/Halide,ayanazmat/Halide,jiawen/Halide,adasworks/Halide,mcanthony/Halide,psuriana/Halide,jiawen/Halide,myrtleTree33/Halide,delcypher/Halide,aam/Halide,dan-tull/Halide,rodrigob/Halide,rodrigob/Halide,tdenniston/Halide,fengzhyuan/Halide,myrtleTree33/Halide,adasworks/Halide,fengzhyuan/Halide,jiawen/Halide,lglucin/Halide,rodrigob/Halide,gchauras/Halide,lglucin/Halide,dougkwan/Halide,kenkuang1213/Halide,adasworks/Halide,ayanazmat/Halide,damienfir/Halide,fengzhyuan/Halide,adasworks/Halide,ronen/Halide,damienfir/Halide,smxlong/Halide,kenkuang1213/Halide,aam/Halide,dan-tull/Halide,psuriana/Halide,dougkwan/Halide,dougkwan/Halide,myrtleTree33/Halide,dan-tull/Halide,jiawen/Halide,fengzhyuan/Halide,fengzhyuan/Halide,lglucin/Halide,damienfir/Halide,kgnk/Halide,gchauras/Halide,dougkwan/Halide,tdenniston/Halide,kgnk/Halide,ronen/Halide,kgnk/Halide,kgnk/Halide,smxlong/Halide,delcypher/Halide,ronen/Halide,dan-tull/Halide,rodrigob/Halide,dougkwan/Halide,fengzhyuan/Halide,kgnk/Halide,ronen/Halide,smxlong/Halide,jiawen/Halide,lglucin/Halide,tdenniston/Halide,mikeseven/Halide,dan-tull/Halide,myrtleTree33/Halide,dan-tull/Halide,damienfir/Halide,lglucin/Halide,mcanthony/Halide,ronen/Halide,psuriana/Halide,psuriana/Halide,mcanthony/Halide,kgnk/Halide,kenkuang1213/Halide,kenkuang1213/Halide,ayanazmat/Halide,rodrigob/Halide,psuriana/Halide,mcanthony/Halide,kenkuang1213/Halide,rodrigob/Halide,mcanthony/Halide,mcanthony/Halide,gchauras/Halide,aam/Halide,kenkuang1213/Halide,lglucin/Halide,kenkuang1213/Halide,ayanazmat/Halide,smxlong/Halide,ayanazmat/Halide,smxlong/Halide,adasworks/Halide,delcypher/Halide,tdenniston/Halide,smxlong/Halide,tdenniston/Halide,dougkwan/Halide,mikeseven/Halide,adasworks/Halide,smxlong/Halide,kgnk/Halide,fengzhyuan/Halide,mcanthony/Halide,kgnk/Halide,aam/Halide,damienfir/Halide,damienfir/Halide,delcypher/Halide,lglucin/Halide,dougkwan/Halide,jiawen/Halide,kenkuang1213/Halide,myrtleTree33/Halide,aam/Halide,ronen/Halide,aam/Halide,psuriana/Halide,mikeseven/Halide,delcypher/Halide,psuriana/Halide,adasworks/Halide,dougkwan/Halide,rodrigob/Halide,mikeseven/Halide,fengzhyuan/Halide,rodrigob/Halide,tdenniston/Halide,delcypher/Halide,myrtleTree33/Halide,dan-tull/Halide,ayanazmat/Halide,gchauras/Halide,smxlong/Halide,delcypher/Halide,damienfir/Halide,adasworks/Halide,mcanthony/Halide,damienfir/Halide,gchauras/Halide,ronen/Halide,ayanazmat/Halide,delcypher/Halide,tdenniston/Halide,gchauras/Halide,ayanazmat/Halide,tdenniston/Halide