goldfish: support system_ext

For sdk_phone_* targets only

Change-Id: I4109a923a53311d09bafc2a0f5a70b2af4509cc3
diff --git a/target/product/sdk_phone_x86.mk b/target/product/sdk_phone_x86.mk
index b34e5b6..b3e205c 100644
--- a/target/product/sdk_phone_x86.mk
+++ b/target/product/sdk_phone_x86.mk
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+QEMU_USE_SYSTEM_EXT_PARTITIONS := true
 
 $(call inherit-product, $(SRC_TARGET_DIR)/product/aosp_x86.mk)