Open java.lang for dokka

Bug: 240421555
Test: m sdk
Change-Id: I38df207ca2c891df24fe32f711b2767cb17195ec
diff --git a/java/droiddoc.go b/java/droiddoc.go
index 9b1f43b..fc95184 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -755,6 +755,7 @@
 	return rule.Command().
 		BuiltTool("dokka").
 		Flag(config.JavacVmFlags).
+		Flag("-J--add-opens=java.base/java.lang=ALL-UNNAMED").
 		Flag(srcJarDir.String()).
 		FlagWithInputList("-classpath ", dokkaClasspath, ":").
 		FlagWithArg("-format ", "dac").