Add libdrmclearkeyplugin.so to image.

The library will be added to /system/vendor/lib/mediadrm.

Change-Id: Iebfd00077c2a13e4ad4296aedba21230a7e4f37f
diff --git a/target/product/base.mk b/target/product/base.mk
index 303818b..3609d03 100644
--- a/target/product/base.mk
+++ b/target/product/base.mk
@@ -48,6 +48,7 @@
     libcamera_client \
     libcameraservice \
     libdl \
+    libdrmclearkeyplugin \
     libeffectproxy \
     libeffects \
     libinput \