Disable verity metadata for eng builds

We don't have dm-verity enabled on eng builds, so don't waste time
generating metadata for images.

Change-Id: Ib2c8d459bb50c30dc32a4ea1fdedc152c09a3a0f
(cherry picked from commit beae6395fc934ae24955a5e96ec04cda5535d952)
diff --git a/target/product/verity.mk b/target/product/verity.mk
index 3e00b49..6676ffe 100644
--- a/target/product/verity.mk
+++ b/target/product/verity.mk
@@ -14,15 +14,19 @@
 # limitations under the License.
 #
 
-# Provides dependencies necessary for verified boot
+# Provides dependencies necessary for verified boot (only for user and
+# userdebug builds)
 
-PRODUCT_SUPPORTS_BOOT_SIGNER := true
-PRODUCT_SUPPORTS_VERITY := true
+user_variant := $(filter user userdebug,$(TARGET_BUILD_VARIANT))
+ifneq (,$(user_variant))
+    PRODUCT_SUPPORTS_BOOT_SIGNER := true
+    PRODUCT_SUPPORTS_VERITY := true
 
-# The dev key is used to sign boot and recovery images, and the verity
-# metadata table. Actual product deliverables will be re-signed by hand.
-# We expect this file to exist with the suffixes ".x509.pem" and ".pk8".
-PRODUCT_VERITY_SIGNING_KEY := build/target/product/security/verity
+    # The dev key is used to sign boot and recovery images, and the verity
+    # metadata table. Actual product deliverables will be re-signed by hand.
+    # We expect this file to exist with the suffixes ".x509.pem" and ".pk8".
+    PRODUCT_VERITY_SIGNING_KEY := build/target/product/security/verity
 
-PRODUCT_PACKAGES += \
-        verity_key
+    PRODUCT_PACKAGES += \
+            verity_key
+endif