getdeps: fix an fbsource invalidation problem

Summary:
When the commit hash changed in fbsource, we would correctly decide
that we'd need to rebuild first-party projects but we would incorrectly skip
running the fetcher.update method.  This would mean that we'd not perform the
shipit run and that our shipit tree would diverge from the source tree.

This commit resolves this by performing the fetcher.update but ignoring
the source update status in this case.

Reviewed By: xavierd

Differential Revision: D21364131

fbshipit-source-id: b4001e549c7d3f27aa4a21b19893c9bb7c0f6d1f

build/fbcode_builder/getdeps.py

@@ -568,6 +568,10 @@ class BuildCmd(ProjectCmdBase):
                     os.unlink(built_marker)
                     reconfigure = True
                     sources_changed = True
+                    # While we don't need to consult the fetcher for the
+                    # status in this case, we may still need to have eg: shipit
+                    # run in order to have a correct source tree.
+                    fetcher.update()
 
             if check_fetcher:
                 change_status = fetcher.update()