Raise minimum supported macOS version to 10.12

Setting of `MACOSX_DEPLOYMENT_TARGET` exposed that some software cannot
actually be built for 10.10, so bump to 10.12 (Sierra).

metapkg/targets/macos/__init__.py

@@ -276,7 +276,7 @@ def min_supported_version(self) -> str:
  if self.machine_architecture_alias == "arm64":
  return "10.15"
  else:
- return "10.10"
+ return "10.12"
 
  def get_package_repository(self) -> MacOSRepository:
  repo = MacOSRepository("macos")