Add an output file tag for proguard dictionaries

Allow modules to depend on the proguard dictionary of another module
using module{.proguard_map}.

Bug: 122332855
Test: m checkbuild
Change-Id: I918b487872c1a8ef8a51c0b994277efb0512d157
diff --git a/java/java.go b/java/java.go
index fea38b5..3b789f6 100644
--- a/java/java.go
+++ b/java/java.go
@@ -370,6 +370,8 @@
 		return append(android.Paths{j.outputFile}, j.extraOutputFiles...), nil
 	case ".jar":
 		return android.Paths{j.implementationAndResourcesJar}, nil
+	case ".proguard_map":
+		return android.Paths{j.proguardDictionary}, nil
 	default:
 		return nil, fmt.Errorf("unsupported module reference tag %q", tag)
 	}