'cflags' parameter is broken in gyp on OS X?

README.md

This is a barebones GYP file to compile 1 C source file. We are demonstrating that the cflags parameter in gyp files gets completely ignored :(

$ ../gyp/gyp -f make --depth=. hello.gyp
$ V=1 make
  cc   -fasm-blocks -mpascal-strings -Os -gdwarf-2  -MMD -MF out/Default/.deps/out/Default/obj.target/hello/hello.o.d.raw  -c -o out/Default/obj.target/hello/hello.o hello.c
  ./gyp-mac-tool flock out/Default/linker.lock g++ -Lout/Default   -o "out/Default/hello" out/Default/obj.target/hello/hello.o 
  LINK(target) out/Default/hello: Finished

We would expect a -ObjC flag to be present somewhere in the cc command, but it's not...

hello.c

#include <stdio.h>

int main () {
  printf("Hello\n");
  return 0;
}

hello.gyp

{
  'targets': [
    {
      'target_name': 'hello',
      'type': 'executable',
      'cflags': [
          '-ObjC'
      ],
      'sources': [
          'hello.c'
      ]
    }
  ]
}

How to make this brilliant utilty pass flag on linux?