check for duplicate call

lam-packaging/debian/minify

@@ -2,6 +2,7 @@
 
 set -e
 outFile=templates/lib/100_lam.${SOURCE_DATE_EPOCH}.min.js
+if [ ! -e $outFile ]; then
 	files=`ls templates/lib/*.js`
 	jsFiles=""
 	for file in $files; do
@@ -11,11 +12,13 @@ closure-compiler --charset UTF-8 $jsFiles --js_output_file $outFile
 	rm $files
 	# add final new line to supress Debian warnings
 	echo "" >> $outFile
+fi
 
 files=`ls style/*.css`
 outFile=style/100_lam.${SOURCE_DATE_EPOCH}.min.css
+if [ ! -e $outFile ]; then
 	cat $files | cleancss -o ${outFile}
 	rm $files
 	# add final new line to supress Debian warnings
 	echo "" >> $outFile
-
+fi