simplify fetch-bundles script

build/builtin-actors/fetch-bundles.sh

@@ -20,12 +20,7 @@ check() {
     file=$1
     hash=$2
     if [ -e "$file" ]; then
-        file_hash=$(sha256sum "$file" | cut -d ' ' -f 1)
+        echo "$hash $file" | sha256sum --check
-        if [ "$file_hash" == "$hash" ]; then
-            return 0
-        else
-            return 1
-        fi
     else
         return 1
     fi