Add a Kati-based packaging step

The idea is that we'd move the installation and packaging tasks over to
it, using data from Soong & the Kati reading Android.mk files.

This would allow us to make more fundamental changes about how we
package things without having to adjust makefiles throughout the tree.
Possible use cases:

* Moving some information from Soong's Android.mk output to a file read
  by the packaging step may allow us to read the Android.mk files less
  often, speeding up builds.

* Refactoring our current two-stage ASAN builds to run the Kati build
  step twice, writing into different object directories, then have a
  single packaging step that reads both outputs. Soong already has the
  capability of writing out a single ninja file with all the asan
  combinations.

* Running two build steps, one building the system-related modules
  using a "generic" device configuration, and one building the vendor
  modules using a specific device configuration. This could enforce a
  GSI/mainline system vs vendor split in a single build invocation.

* If all installation is through this tool, it will be much easier to
  track what should no longer be installed on an incremental build,
  reducing the need for installclean.

* Changing PRODUCT_PACKAGES should be a much faster operation, which
  means we could keep track of local additions to the images. Then
  `mma` would be more persistent, instead of installing something once,
  then never updating it again.

Eventually we plan on switching from Kati to something Go-based, but
this is a more incremental approach while we clean up everything else.

Currently, this just moves the dist-for-goal handling over to the
packaging step, so that we don't need to read Android.mk files when
DIST_DIR changes, or we switch between dist vs not.

Bug: 116968624
Bug: 117463001
Test: m nothing
Change-Id: Idec5ac6f7c7475397ba0fb65bd3785128a7517df
diff --git a/ui/build/build.go b/ui/build/build.go
index 377481b..c902a0f 100644
--- a/ui/build/build.go
+++ b/ui/build/build.go
@@ -40,9 +40,10 @@
 pool local_pool
  depth = {{.Parallel}}
 build _kati_always_build_: phony
-{{if .HasKatiSuffix}}include {{.KatiBuildNinjaFile}}
+{{if .HasKatiSuffix}}subninja {{.KatiBuildNinjaFile}}
+subninja {{.KatiPackageNinjaFile}}
 {{end -}}
-include {{.SoongNinjaFile}}
+subninja {{.SoongNinjaFile}}
 `))
 
 func createCombinedBuildNinjaFile(ctx Context, config Config) {
@@ -180,6 +181,7 @@
 		genKatiSuffix(ctx, config)
 		runKatiCleanSpec(ctx, config)
 		runKatiBuild(ctx, config)
+		runKatiPackage(ctx, config)
 
 		ioutil.WriteFile(config.LastKatiSuffixFile(), []byte(config.KatiSuffix()), 0777)
 	} else {