Fix emul-ezt to not choke on Java 8 emul classes

Note that emul-ezt needs to run with Java 8 to be able to analyze
the emul sources.

Change-Id: Ibf1bf556071440f3de868116e2d55107a1be1118
diff --git a/build_tools/doctool/src/com/google/doctool/JreDocTool.java b/build_tools/doctool/src/com/google/doctool/JreDocTool.java
index 40b7b5c..55195bf 100644
--- a/build_tools/doctool/src/com/google/doctool/JreDocTool.java
+++ b/build_tools/doctool/src/com/google/doctool/JreDocTool.java
@@ -139,7 +139,7 @@
     args.add("-quiet");
 
     args.add("-source");
-    args.add("1.5");
+    args.add("1.8");
 
     args.add("-doclet");
     args.add(EztDoclet.class.getName());