po/make_pot: sort lua files in POT

find may output matching files in any order.
To avoid unnecessary changes between regeneration
sort its output. For C++ sources xgettext’s --sort-by-file
already has an equivalent effect. All other files are already
statically listed in a fixed order.

Adopts part of: 4aee271d03

po/make_pot.sh

@@ -35,6 +35,7 @@ grep '"[A-Za-z ]\+" : {' -n ../src/libresrc/default_hotkey.json \
   | maybe_append
 
 find ../automation -name *.lua \
+  | LC_ALL=C sort \
   | xargs grep tr\"[^\"]\*\" -o -n \
   | sed 's/\(.*\):\([0-9]\+\):tr\(".*"\)/\1|\2|\3/' \
   | sed 's/\\/\\\\\\\\/g' \