forall: use a generator to map the Pool

Before, a list was generated, which is why there was a massive delay.

Using a generator will allow processes to start straight away

Change-Id: Ia325b0b340cc328c08c9bcc92a6709bbdaf6a664

subcmds/forall.py

@@ -212,8 +212,8 @@ without iterating through the remaining projects.
       config = self.manifest.manifestProject.config
       results_it = pool.imap(
          DoWorkWrapper,
-         [[mirror, opt, cmd, shell, cnt, config, self._SerializeProject(p)]
-          for cnt, p in enumerate(projects)]
+         ([mirror, opt, cmd, shell, cnt, config, self._SerializeProject(p)]
+          for cnt, p in enumerate(projects))
       )
       pool.close()
       for r in results_it: