Fix BOARD_SYSTEMSDK_VERSIONS checks

BOARD_SYSTEMSDK_VERSIONS must be greater than or equal to the minimum
of PRODUCT_SHIPPING_API_LEVEL and BOARD_API_LEVEL. If BOARD_API_LEVEL
is not defined, read BOARD_SHIPPING_API_LEVEL. If both board api
levels are not defined, compare only with PRODUCT_SHIPPING_API_LEVEL.

Bug: 204964200
Bug: 201489975
Bug: 202919753
Test: manual test with different settings
Change-Id: I36fa0b2fed3bca9ebe1baad46ee1dbe8cb1414e3