Make compress.sh POSIX compliant instead

compress.sh

@@ -1,19 +1,6 @@
-#!/bin/bash
+#!/bin/sh
 
 files=$(find public/ -name "*.html" -o -name "*.xml" -o -name "*.css" -o -name "*.js")
 
-gz() {
-    echo "GZIP $1"
-    gzip -fnk $1
-}
-
-br() {
-    echo "BROTLI $1"
-    brotli -fZk $1
-}
-
-export -f gz
-export -f br
-
-parallel $@ gz {} <<< $files
-parallel $@ br {} <<< $files
+printf '%s\n' "$files" | parallel $@ "echo 'GZIP {}' && gzip -fnk {}"
+printf '%s\n' "$files" | parallel $@ "echo 'BROTLI {}' && brotli -fZk {}"