message: Use -Wno-sign-compare to make recent GCC happy
diff: @@ -136,7 +136,7 @@ def build(bld):
  bld.program(
  source=cc_files,
  - cxxflags=['-g', '-O3', '-std=c++11', '-Wall', '-Werror'],
  + cxxflags=['-g', '-O3', '-std=c++11', '-Wall', '-Wno-sign-compare', '-Werror'],
  includes=[
  'third_party/',
  'third_party/doctest/',
  