libbpf: install the header file libbpf.h

It seems like an oversight not to install the header file for libbpf,
given the libbpf.so + libbpf.a files are installed.
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/lib/bpf/Makefile

@@ -192,7 +192,8 @@ install_lib: all_cmd
 
 install_headers:
 	$(call QUIET_INSTALL, headers) \
-		$(call do_install,bpf.h,$(prefix)/include/bpf,644)
+		$(call do_install,bpf.h,$(prefix)/include/bpf,644); \
+		$(call do_install,libbpf.h,$(prefix)/include/bpf,644);
 
 install: install_lib