build: avoid updated PO files being remerged upon every make

po/update_linguas.sh

@@ -18,6 +18,9 @@ fi
 echo "Regenerating POT file and remerging and recompiling PO files..."
 make update-po
 
+# Ensure that the PO files are newer than the POT.
+touch *.po
+
 # If needed, fix a problem in the Makefile template.
 grep -q '^datarootdir' Makefile.in.in || \
 	sed -i 's/^\(datadir.*\)/datarootdir = @datarootdir@\n\1/' Makefile.in.in