Add support for remote-execution / caching of signapk actions

Test: "RBE_SIGNAPK=true RBE_SIGNAPK_EXEC_STRATEGY=remote ... use_rbe m" on crosshatch-userdebug and
signapk targets worked
Bug: b/156765091

Change-Id: I4b8c21320c2f38914ef39d3d8f036d885fab4e72
diff --git a/apex/builder.go b/apex/builder.go
index 11652bc..a6a347b 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -582,19 +582,27 @@
 	}
 
 	a.outputFile = android.PathForModuleOut(ctx, a.Name()+suffix)
+	rule := java.Signapk
+	args := map[string]string{
+		"certificates": a.container_certificate_file.String() + " " + a.container_private_key_file.String(),
+		"flags":        "-a 4096", //alignment
+	}
+	implicits := android.Paths{
+		a.container_certificate_file,
+		a.container_private_key_file,
+	}
+	if ctx.Config().IsEnvTrue("RBE_SIGNAPK") {
+		rule = java.SignapkRE
+		args["implicits"] = strings.Join(implicits.Strings(), ",")
+		args["outCommaList"] = a.outputFile.String()
+	}
 	ctx.Build(pctx, android.BuildParams{
-		Rule:        java.Signapk,
+		Rule:        rule,
 		Description: "signapk",
 		Output:      a.outputFile,
 		Input:       unsignedOutputFile,
-		Implicits: []android.Path{
-			a.container_certificate_file,
-			a.container_private_key_file,
-		},
-		Args: map[string]string{
-			"certificates": a.container_certificate_file.String() + " " + a.container_private_key_file.String(),
-			"flags":        "-a 4096", //alignment
-		},
+		Implicits:   implicits,
+		Args:        args,
 	})
 
 	// Install to $OUT/soong/{target,host}/.../apex