Enable JIT Zygote experiment in mainline boardconfig

Like Ie413f84c545c869ee336912a7b05ca80bb968129, but for all
mainline devices.

Bug: 119800099
Test: m
Change-Id: Ief77adaea61203a013f85cf870c5350253fdb7dd
diff --git a/target/board/BoardConfigMainlineCommon.mk b/target/board/BoardConfigMainlineCommon.mk
index 8d2957c..6c56671 100644
--- a/target/board/BoardConfigMainlineCommon.mk
+++ b/target/board/BoardConfigMainlineCommon.mk
@@ -41,3 +41,6 @@
 
 # Enable system property split for Treble
 BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED := true
+
+# Generate an APEX image for experiment b/119800099.
+DEXPREOPT_GENERATE_APEX_IMAGE := true