not very useful without tools, and the contrib Makefile has a gnu-ism

Index: Makefile.in
--- Makefile.in.orig
+++ Makefile.in
@@ -450,7 +450,7 @@ top_srcdir = @top_srcdir@
 # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 SUBDIRS = lib third-party src bpf examples tests integration-tests \
-	doc contrib script
+	doc script
 
 ACLOCAL_AMFLAGS = -I m4
 dist_doc_DATA = README.rst