AAPT leave <gradient> alone for VDC

bug: 62421666
Test: Tested with changes for Gradient of VDC.

Change-Id: I07b39721aeaaafd888416a0f71f6cbd5fce97732
diff --git a/tools/aapt2/cmd/Link.cpp b/tools/aapt2/cmd/Link.cpp
index 88e0f69..d7d1d3e 100644
--- a/tools/aapt2/cmd/Link.cpp
+++ b/tools/aapt2/cmd/Link.cpp
@@ -446,7 +446,7 @@
 
 static bool IsVectorElement(const std::string& name) {
   return name == "vector" || name == "animated-vector" || name == "pathInterpolator" ||
-         name == "objectAnimator";
+         name == "objectAnimator" || name == "gradient";
 }
 
 template <typename T>