CGRPC is a Swift 3.0 wrapper for the C core library of GRPC. A working installation of GRPC is required; pkg-config should be able to generate the correct CFLAGS and LDFLAGS for using the library.
The Swift front-end currently does not allow an imported module to include pthread.h; it will complain about symbol redefinition, because libpthread symbols are automatically imported by default. We work around this by modifying the GRPC headers to remove references to pthread.h. You can do this during installation by applying the patch grpc-header-hack.diff to the GRPC installation:
cd /usr/local/include
sudo patch -p1 < ~/CGRPC/grpc-header-hack.diff