Run the Finder and make its results available to Kati

The Finder runs roughly 200ms faster than findleaves.py in aosp,
and runs roughly 400ms faster in internal master.

Bug: 64363847
Test: m -j

Change-Id: I62db8dacc90871e913576fe2443021fb1749a483
diff --git a/cmd/soong_ui/main.go b/cmd/soong_ui/main.go
index 94d6d5c..8a26171 100644
--- a/cmd/soong_ui/main.go
+++ b/cmd/soong_ui/main.go
@@ -95,5 +95,9 @@
 		}
 	}
 
+	f := build.NewSourceFinder(buildCtx, config)
+	defer f.Shutdown()
+	build.FindSources(buildCtx, config, f)
+
 	build.Build(buildCtx, config, build.BuildAll)
 }