Fix the self update for macOS so that the installer is executed

Author: cmcgee1024

Sources/MacOSPlatform/MacOS.swift

@@ -117,10 +117,10 @@ public struct MacOS: Platform {
 
  if ctx.mockedHomeDir == nil {
  await ctx.message("Extracting the swiftly package...")
- _ = sys.installer(
+ try await sys.installer(
  .pkg(archive),
  .target("CurrentUserHomeDirectory")
- )
+ ).run(self)
  try? await sys.pkgutil(.volume(userHomeDir)).forget(pkg_id: "org.swift.swiftly").run(self)
  } else {
  let installDir = userHomeDir / ".swiftly"