build: clean up the generated tap file

Make `make clean` cleanup the generated tap file as well.

Fixes: #2834

PR-URL: #2837
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Alexis Campailla <orangemocha@nodejs.org>

Makefile

@@ -69,6 +69,7 @@ clean:
 	-rm -rf out/Makefile $(NODE_EXE) $(NODE_G_EXE) out/$(BUILDTYPE)/$(NODE_EXE)
 	@if [ -d out ]; then find out/ -name '*.o' -o -name '*.a' | xargs rm -rf; fi
 	-rm -rf node_modules
+	-rm -f test.tap
 
 distclean:
 	-rm -rf out