Keep trying to fix (#344)

Co-authored-by: Oscar Boykin <oboykin@netflix.com>

Author: johnynek

ci_scripts/prepare_output.sh

@@ -6,7 +6,7 @@ OUTPUT_PATH=$3
 
 GENERATED_SHA_256=$(shasum -a 256 $BINARY | awk '{print $1}')
 
-mkdir $OUTPUT_PATH
+mkdir -p $OUTPUT_PATH
 
 cp $BINARY $OUTPUT_PATH/${ARTIFACT_NAME}
 echo $GENERATED_SHA_256 > $OUTPUT_PATH/${ARTIFACT_NAME}.sha256