message: cxx: Fix use_whole_archive support on macos: use linker -all_load option.
diff: @@ -880,6 +880,9 @@ class GccToolkit(Toolkit):
  libraries = (obj for obj in objs if isinstance(obj, Library))
  self.__libraries_flags(cfg, libraries, cmd)
  if cfg.whole_archive:
  + if self.os is drake.os.macos:
  + cmd += '-Wl,-all_load' # close enough
  + else:
  pre=list()
  ar=list()
  post=list()
  @@ -925,6 +928,9 @@ class GccToolkit(Toolkit):
  cmd += ['-shared', '-o', exe.path()]
  self.__libraries_flags(cfg, to_link, cmd)
  if cfg.whole_archive:
  + if self.os is drake.os.macos:
  + cmd += '-Wl,-all_load' # close enough
  + else:
  pre=list()
  ar=list()
  post=list()
  