scripts/build: parallelize compression better

scripts/build

@@ -4,12 +4,12 @@ cd "$(git rev-parse --show-toplevel)"
 
 hugo --cleanDestinationDir --printPathWarnings --panicOnWarning
 
-cd public
-
-find . \
+find public \
     -name '*.html' -or \
     -name '*.xml' -or \
     -name '*.txt' -or \
     -name '*.css' -or \
     -name '*.map' -or \
-    -name '*.pdf' | parallel --eta "zopfli {} && brotli {}"
+    -name '*.pdf' | \
+    awk '{print "zopfli "$0;print "brotli "$0}' | \
+      xargs -P$(nproc) -I{} $SHELL -c {}