Set ro.llndk.api_level as a system prop

ro.llndk.api_level is included in system/build.prop.
It must have the system build_prop context instead of the vendor prop.

Bug: 312098788
Test: TH
Change-Id: I223ae2cd56490a2cfd6f6454ad685d23d90d9329
diff --git a/private/property_contexts b/private/property_contexts
index aa15633..a798d11 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -1152,7 +1152,7 @@
 ro.board.first_api_level u:object_r:build_vendor_prop:s0 exact int
 ro.board.api_level       u:object_r:build_vendor_prop:s0 exact int
 ro.board.api_frozen      u:object_r:build_vendor_prop:s0 exact bool
-ro.llndk.api_level       u:object_r:build_vendor_prop:s0 exact int
+ro.llndk.api_level       u:object_r:build_prop:s0 exact int
 ro.vendor.api_level      u:object_r:build_vendor_prop:s0 exact int
 
 # Boot image build props set by /{second_stage_resources/,}boot/etc/build.prop