Default undefined PRODUCT_SHIPPING_API_LEVEL to fake treble

This is a temporary measure to disable treble sepolicy tests for
non-compliant targets.

Bug: 113124961
Bug: 111243627
Test: m selinux_policy
Change-Id: I291b7cc3c8c07b838f1ea22e55550c42c5083d8f

treble_sepolicy_tests_for_release.mk

@@ -89,7 +89,11 @@ $(treble_sepolicy_tests_$(version)): PRIVATE_PLAT_SEPOLICY := $(built_plat_sepol
 $(treble_sepolicy_tests_$(version)): PRIVATE_PLAT_PUB_SEPOLICY := $(base_plat_pub_policy.cil)
 $(treble_sepolicy_tests_$(version)): PRIVATE_FAKE_TREBLE :=
 ifeq ($(PRODUCT_FULL_TREBLE_OVERRIDE),true)
-ifdef PRODUCT_SHIPPING_API_LEVEL
+# TODO(b/113124961): undefined PRODUCT_SHIPPING_API_LEVEL should default to full
+# Treble. Change the behavior once the bug is fixed.
+ifndef PRODUCT_SHIPPING_API_LEVEL
+$(treble_sepolicy_tests_$(version)): PRIVATE_FAKE_TREBLE := --fake-treble
+else
 # These requirements were originally added in Android Oreo. Devices
 # launching after this should not distinguish between
 # PRODUCT_FULL_TREBLE and PRODUCT_FULL_TREBLE_OVERRIDE since this could