build.py uses ninja build (#200)
build.py uses ninja build (#200)

* build.py uses ninja build

* move use of Ninja to non-Windows build

jbcoe/C_API_generation,FFIG/ffig,FFIG/ffig,FFIG/ffig,FFIG/ffig,FFIG/ffig,FFIG/ffig,jbcoe/C_API_generation,jbcoe/C_API_generation,jbcoe/C_API_generation,FFIG/ffig,FFIG/ffig