bpf_module_test - add extra assert to pre-verify bpf .o file existence

This results in a much clearer error:
  test/vts-testcase/kernel/api/bpf_native_test/BpfTest.cpp:137: Failure
  Expected equality of these values:
  0
  access(progSrcPath.c_str(), 4) ? (*__errno()) : 0
  Which is: 2

Instead of a 0 != -1 failure on android::bpf::loadProg(progSrcPath.c_str())

Test: 'atest bpf_module_test' fails more clearly
Bug: 141939927
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I7d018a3ea7df713d0f60fba930de80ddec5d8d5c
1 file changed