Tweak packaging script

Makefile

@@ -61,7 +61,7 @@ setup:
 
 clean:
 	rm -f ./pgweb
-	rm -f ./bin/*
+	rm -rf ./bin/*
 	rm -f bindata.go
 	make assets
 

script/package.sh

@@ -3,12 +3,12 @@
 set -e
 
 DIR="./bin"
-rm $DIR/*.zip
+rm -f $DIR/*.zip
 
 for file in $(ls $DIR)
 do
   fin=$DIR/$file
   fout=$DIR/$file.zip
   shasum -a 256 $fin
-  zip -9 -q $fout $fin
+  zip -9 -q -j $fout $fin
 done