How to drop third party jars from obfuscated jar using proguard, gradle

Question

I'm using -libraryjar as dependency to obfuscate my android library jar like this:

-injars      build/libs/mylib.jar
-outjars     build/libs/mylib-proguarded.jar
-libraryjars build/intermediates/classes/release/libs/gson-2.3.1.jar

This bundles gson library with final obfuscated library jar.

Issue: The Android app that's supposed to be using obfuscated library jar, has its own inclusion of gson, and I get conflict for having two copies of gson jars. How can I exclude gson jar from library obfuscated jar.

My rest of the proguard config look like this:

-dontpreverify
-dontwarn android.annotation.SuppressLint
-keepparameternames
-renamesourcefileattribute SourceFile
-keepattributes *Annotation*,Exceptions,InnerClasses,Signature,Deprecated,SourceFile,LineNumberTable,*Annotation*,EnclosingMethod

-keep class sun.misc.Unsafe { *; }

-keep public class * {
    public protected *;
}

-keepclassmembernames class * {
    java.lang.Class class$(java.lang.String);
    java.lang.Class class$(java.lang.String, boolean);
}

-keepclasseswithmembernames,includedescriptorclasses class * {
    native <methods>;
}

-keepclassmembers,allowoptimization enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keepclassmembers class * implements java.io.Serializable {
    static final long serialVersionUID;
    private static final java.io.ObjectStreamField[] serialPersistentFields;
    private void writeObject(java.io.ObjectOutputStream);
    private void readObject(java.io.ObjectInputStream);
    java.lang.Object writeReplace();
    java.lang.Object readResolve();
}