Add R8 support

Add support for R8 to optimize apps and java libraries.

Test: m checkbuild
Change-Id: I2afd5d7a84912d3ab613c32c599bd1ebe60562e0
diff --git a/java/androidmk.go b/java/androidmk.go
index 24fe43a..64ef505 100644
--- a/java/androidmk.go
+++ b/java/androidmk.go
@@ -165,6 +165,9 @@
 				if app.jacocoReportClassesFile != nil {
 					fmt.Fprintln(w, "LOCAL_SOONG_JACOCO_REPORT_CLASSES_JAR :=", app.jacocoReportClassesFile.String())
 				}
+				if app.proguardDictionary != nil {
+					fmt.Fprintln(w, "LOCAL_SOONG_PROGUARD_DICT :=", app.proguardDictionary.String())
+				}
 
 				if app.Name() == "framework-res" {
 					fmt.Fprintln(w, "LOCAL_MODULE_PATH := $(TARGET_OUT_JAVA_LIBRARIES)")