add support for marking ebpf programs as being only for some kernel versions

Some ebpf code cannot be loaded on too old kernels.

Sometimes we want a different - more advanced - version of an ebpf program
to be loaded on a newer kernel.

Test: build, atest
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I9e93e7246951916e6d60544575337a7a19c82886
diff --git a/libbpf_android/include/bpf/BpfUtils.h b/libbpf_android/include/bpf/BpfUtils.h
index 06dcc47..f724f3b 100644
--- a/libbpf_android/include/bpf/BpfUtils.h
+++ b/libbpf_android/include/bpf/BpfUtils.h
@@ -148,6 +148,7 @@
 uint64_t getSocketCookie(int sockFd);
 int synchronizeKernelRCU();
 int setrlimitForTest();
+unsigned kernelVersion();
 std::string BpfLevelToString(BpfLevel BpfLevel);
 BpfLevel getBpfSupportLevel();