NetBpfLoad: introduce APEXROOT/BPFROOT defines

This allows changing the location of bpf programs easily
when building for the host to run on UML as a test.

Bug: 205608149
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I24816b6660581e74f277df39495a43027b77d2cf
1 file changed