Print a status message when starting ninja

This way we don't appear hung at:

  No need to regenerate ninja file

Change-Id: I8dbdaa2c1b1c5a6a73187d0e6061f363b62e10c9
Fixes: 122251150
Test: m nothing

ui/build/ninja.go

@@ -97,6 +97,7 @@ func runNinja(ctx Context, config Config) {
 		}
 	}()
 
+	ctx.Status.Status("Starting ninja...")
 	cmd.RunAndPrintOrFatal()
 }
 

ui/status/status.go

@@ -260,6 +260,10 @@ func (s *Status) message(level MsgLevel, msg string) {
 	}
 }
 
+func (s *Status) Status(msg string) {
+	s.message(StatusLvl, msg)
+}
+
 type toolStatus struct {
 	status *Status