Respect VABC Xor prop in ota_from_target_files

Test: generate ota on a non-vabc xor target, make sure it's not used
Change-Id: Ibdbcfe3775c96848c37c7f580121583d4bd57fce
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 97cfee9..f30e382 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -449,6 +449,13 @@
     return vabc_enabled
 
   @property
+  def is_vabc_xor(self):
+    vendor_prop = self.info_dict.get("vendor.build.prop")
+    vabc_xor_enabled = vendor_prop and \
+        vendor_prop.GetProp("ro.virtual_ab.compression.xor.enabled") == "true"
+    return vabc_xor_enabled
+
+  @property
   def vendor_suppressed_vabc(self):
     vendor_prop = self.info_dict.get("vendor.build.prop")
     vabc_suppressed = vendor_prop and \