Ensure that 'comm' input is sorted.

The requirements file needs to be sorted in order to be compared
sensibly.

perl-env-setup

@@ -226,7 +226,7 @@ function install_requirements() {
             local -a toinstall
             local def="${required_defs[$defindex]}"
             local depfile="${environment}/${def}.deps"
-            toinstall=($(comm -12 <(sed 's/[~@].*$//' "$reqfile") "$depfile"))
+            toinstall=($(comm -12 <(sed 's/[~@].*$//' "$reqfile" | sort) "$depfile"))
             debug "  Checking $defindex - $def: ${toinstall[*]}"
 
             local -a promotedef