bug fix in apt install

Makefile

@@ -7,7 +7,7 @@
 all : makestamps/apt makestamps/yum makestamps/pip buttersink/version.py
 
 makestamps/apt : apt.txt | makestamps
-	if [ -f "/etc/debian_version" ]; then sudo apt-get install $$(cat $<) touch $@ ; fi
+	if [ -f "/etc/debian_version" ]; then sudo apt-get install -y $$(cat $<); touch $@ ; fi
 
 makestamps/yum : yum.txt | makestamps
 	if [ -f "/etc/redhat-release" ]; then sudo yum install -y $$(cat $<); touch $@ ; fi