message: zlib: turn warnings off
  And factor the definitions of CC and CFLAGS.
diff: @@ -256,20 +256,16 @@ def configure(cxx_toolkit = None,
  zlib_configure_call = None
  zlib_configure_args = ['--static']
  else:
  - zlib_env['CFLAGS'] = '-fPIC'
  + zlib_env['CC'] = cxx_toolkit.c
  + zlib_env['CFLAGS'] = '-fPIC -w'
  zlib_makefile = None
  zlib_configure_call = zlib_configure
  zlib_configure_args = []
  - if cxx_toolkit.architecture is drake.architecture.arm:
  - zlib_env['CC'] = cxx_toolkit.cxx[:-4] + '-gcc'
  if cxx_toolkit.os is drake.os.macos:
  - zlib_env['CC'] = cxx_toolkit.c
  zlib_lib = drake.cxx.DynLib('zlib/lib/libz.%s.dylib' % zlib_version)
  elif cxx_toolkit.os in [drake.os.linux]:
  - zlib_env['CC'] = cxx_toolkit.c
  zlib_lib = drake.cxx.DynLib('zlib/lib/libz.so.1')
  elif cxx_toolkit.os is drake.os.android:
  - zlib_env['CC'] = cxx_toolkit.c
  zlib_lib = drake.cxx.StaticLib('zlib/lib/libz.a')
  zlib_configure_args = ['--static']
  elif cxx_toolkit.os is drake.os.ios:
  @@ -277,16 +273,16 @@ def configure(cxx_toolkit = None,
  zlib_arch_str = ''
  for arch in archs:
  zlib_arch_str += '-arch %s ' % arch
  - zlib_env['CC'] = '%s %s -mios-version-min=7.0' % (cxx_toolkit.c, zlib_arch_str)
  + zlib_env['CC'] += ' %s -mios-version-min=7.0' % (zlib_arch_str)
  zlib_env['SDKROOT'] = os.environ['SDKROOT']
  - zlib_env['CFLAGS'] = '-fPIC -isysroot %s' % os.environ['SDKROOT']
  + zlib_env['CFLAGS'] += ' -isysroot %s' % os.environ['SDKROOT']
  zlib_libs = [zlib_lib,]
  zlib_prefix_absolute = drake.path_build(zlib_prefix,
  absolute = True)
  zlib_args = [
  - "INCLUDE_PATH='%s/include'" % zlib_prefix_absolute,
  "BINARY_PATH='%s/bin'" % zlib_prefix_absolute,
  + "INCLUDE_PATH='%s/include'" % zlib_prefix_absolute,
  "LIBRARY_PATH='%s/lib'" % zlib_prefix_absolute,
  ]
  if windows:
  