Keep class file version during shrinking; generate Java 8 bytecode

sometimes

build.xml

@@ -28,7 +28,8 @@
     <property name="protobuf-lite.jar" value="${basedir}/dependencies/protobuf-2.6.1-lite.jar"/>
     <property name="javax.inject.jar" value="${basedir}/lib/javax.inject.jar"/>
 
-    <property name="java.target" value="1.6"/>
+    <property name="java.target" value="1.8"/>
+    <property name="java.target.1.6" value="1.6"/>
 
     <condition property="bootstrap.or.local.build" value="true">
         <or>
@@ -1014,7 +1015,7 @@
             </java>
 
             <javac2 srcdir="${toString:src.dirset}" destdir="@{output}" debug="true" debuglevel="lines,vars,source"
-                    includeAntRuntime="false" source="${java.target}" target="${java.target}">
+                    includeAntRuntime="false" source="${java.target.1.6}" target="${java.target.1.6}">
                 <skip pattern="kotlin/Metadata"/>
                 <classpath>
                     <path refid="classpath.path"/>

compiler/compiler.pro

@@ -56,7 +56,6 @@ messages/**)
 -libraryjars '<bootstrap.reflect>'
 -libraryjars '<bootstrap.script.runtime>'
 
--target 1.6
 -dontoptimize
 -dontobfuscate