Support disting in soong-only builds

Disting was normally handled by the packaging kati step, which was
not run in soong-only builds. Disting needs to be done in a separate
ninja file, so that if you toggle dist on/off you only need to
regenerate a small ninja file instead of the main one.

This change makes it so that the kati packaging step is also run in
soong-only builds. (which makes them not technically soong-only, but
the packaging step is very fast so it's fine)

Phonies in soong were normally exported to the main make invocation
and then make would emit the ninja rules for them. In soong-only builds
soong would emit the ninja phone rules directly. This is problematic
when supporting disting in soong, because some of the phony rules have
the same name as dist targets, causing ninja to complain about duplicate
rules. To resolve this, make soong export its phonies to the packaging
step, which will dedup them with the dist phonies.

Bug: 388312357
Test: m --soong-only dist
Change-Id: If6de8c28274fe96dac674f449b9bc0b488540655
diff --git a/android/phony.go b/android/phony.go
index f8db88d..7bdd9d3 100644
--- a/android/phony.go
+++ b/android/phony.go
@@ -15,6 +15,7 @@
 package android
 
 import (
+	"strings"
 	"sync"
 
 	"github.com/google/blueprint"
@@ -68,13 +69,25 @@
 	}
 
 	if !ctx.Config().KatiEnabled() {
+		// In soong-only builds, the phonies can conflict with dist targets that will
+		// be generated in the packaging step. Instead of emitting a blueprint/ninja phony directly,
+		// create a makefile that defines the phonies that will be included in the packaging step.
+		// Make will dedup the phonies there.
+		var buildPhonyFileContents strings.Builder
 		for _, phony := range p.phonyList {
-			ctx.Build(pctx, BuildParams{
-				Rule:      blueprint.Phony,
-				Outputs:   []WritablePath{PathForPhony(ctx, phony)},
-				Implicits: p.phonyMap[phony],
-			})
+			buildPhonyFileContents.WriteString(".PHONY: ")
+			buildPhonyFileContents.WriteString(phony)
+			buildPhonyFileContents.WriteString("\n")
+			buildPhonyFileContents.WriteString(phony)
+			buildPhonyFileContents.WriteString(":")
+			for _, dep := range p.phonyMap[phony] {
+				buildPhonyFileContents.WriteString(" ")
+				buildPhonyFileContents.WriteString(dep.String())
+			}
+			buildPhonyFileContents.WriteString("\n")
 		}
+		buildPhonyFile := PathForOutput(ctx, "soong_phony_targets.mk")
+		writeValueIfChanged(ctx, absolutePath(buildPhonyFile.String()), buildPhonyFileContents.String())
 	}
 }