Some rm commands are not GNU rm.

--- py3c-1.4/Makefile.orig
+++ py3c-1.4/Makefile
@@ -27,10 +27,10 @@
 # TODO: A better way to build & use one-off extensions?
 
 build-%:
-	cd test; rm -rvf ${_testbuilddir_abs} ; $* setup.py build -b ${_testbuilddir_abs}
+	cd test; rm -rf ${_testbuilddir_abs} ; $* setup.py build -b ${_testbuilddir_abs}
 
 build-%-cpp:
-	cd test; rm -rvf ${_testbuilddir_abs} ; TEST_USE_CPP=yes $* setup.py build -b ${_testbuilddir_abs}
+	cd test; rm -rf ${_testbuilddir_abs} ; TEST_USE_CPP=yes $* setup.py build -b ${_testbuilddir_abs}
 
 test-%: build-%
 	echo ${_testbuilddir_abs}