Add PRODUCT_FULL_TREBLE.

PRODUCT_FULL_TREBLE: whether the device has Treble fully enabled (no
passthrough hals, vendor.img, split sepolicy, etc..)

PRODUCT_FULL_TREBLE_OVERRIDE: used if someone wants to consider a device
as full Treble even if it didn't launch with Android O.

Bug: 35809750
Test: PRODUCT_FULL_TREBLE set appropriately with
PRODUCT_FULL_TREBLE_OVERRIDE and PRODUCT_SHIPPING_API_LEVEL = 24/25

Change-Id: I069448beaf26c70acb6c45d4228d8fdfe9476410
diff --git a/core/main.mk b/core/main.mk
index 739fc11..7433f90 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -343,6 +343,16 @@
   ADDITIONAL_BUILD_PROPERTIES += ro.bionic.ld.warning=1
 endif
 
+# Boolean variable determining if Treble is fully enabled
+PRODUCT_FULL_TREBLE := false
+ifeq ($(PRODUCT_FULL_TREBLE_OVERRIDE),true)
+  PRODUCT_FULL_TREBLE := true
+else ifeq ($(PRODUCT_SHIPPING_API_LEVEL),)
+  #$(warning no product shipping level defined)
+else ifneq ($(call math_gt_or_eq,$(PRODUCT_SHIPPING_API_LEVEL),26),)
+  PRODUCT_FULL_TREBLE := true
+endif
+
 # -----------------------------------------------------------------
 ###
 ### In this section we set up the things that are different