Add JSON prebuilt

Change-Id: I4aa75b3690b049d53097e5868f64958547974992
diff --git a/common/json/PREBUILT b/common/json/PREBUILT
new file mode 100644
index 0000000..810d775
--- /dev/null
+++ b/common/json/PREBUILT
@@ -0,0 +1,4 @@
+The object in this prebuilt directory can be rebuilt from
+	platform/libcore/json
+
+From the revision 999187657af9408e86ae680be1f19f184512d210