vars = Variables()vars.Add(PackageVariable('boost', 'boost installation directory (should contain boost/ and lib/)', 'yes'))vars.Add('compiler', 'compiler command to use', 'g++') env = Environment(variables = vars) if env['boost'] == True:  dir = '/usr/local/include'  env['boost'] = dir  if env['boost']:  env.Append(CPPPATH='$boost/include')  env.Append(LIBPATH='$boost/lib') env.Replace(CXX = '$compiler') Help(vars.GenerateHelpText(env)) target = 'bawt'buildDirectory = '.build'SConscript('src/SConscript', exports='env target', variant_dir = buildDirectory , duplicate = 0 ) Clean('.', Glob("*~") + Glob('*/*~') + [ buildDirectory ] )