Define ro.board.api_level property

ro.board.api_level shows the current vendor api level under GRF.
It can be manually defined by setting BOARD_API_LEVEL. Unless
BOARD_API_LEVEL is defined, the ro.board.api_level property will be
defined automatically based on BOARD_SHIPPING_API_LEVEL and
PLATFORM_SDK_VERSION.

Bug: 176950752
Test: getprop ro.board.api_level
Change-Id: I03eeec8d8206abdd0565423d1b6a507d86d9b168
1 file changed