Log file r/w permissions (configured via "mode") are not set correctly when "compress" is set to "true".

How to reproduce:

1. Create "index.js" with this code:

'use strict';

const log4js = require('log4js');

// default log4js configuration: log everything to the console
const LOG4JS_CONFIGURATION_DEFAULT =
  {
    "appenders": {
      "console": {
        "type": "console"
      },
      "file": {
        "type": "dateFile",
        "filename": "my-logger.log",
        "pattern": ".yyyy-MM-dd",
        "mode": 384,
        "mode-comment": "mode 384 is the decimal value of octal 0600",
        "daysToKeep": 30,
        "compress": true
      }
    },
    "categories": {
      "default": {
        "appenders": ["console", "file"],
        "level": "trace"
      }
    }
  };

// apply default configuration
log4js.configure(LOG4JS_CONFIGURATION_DEFAULT);

async function main() {
  let logger = log4js.getLogger('my-logger');
  logger.info('some log');
  await log4js.shutdown();
}

main()
.catch((err) => console.error(err));

2. Run

$ node index.js

and then

$ ls -l

to get

-rw------- 1 morten morten 54 Sep 3 14:23 my-logger.log

Note the "-rw-------" part, which means read/write only for me ("morten"). That matches my mode config in the code, so all good.

3. Run

$ touch -d "24 hours ago" my-logger.log

to change the file date back 24 hours (to force compression in step 4 below).

and then

$ ls -l

to get

-rw------- 1 morten morten 54 Sep 2 14:26 my-logger.log

Note that "Sep 3" changed to "Sep 2" as expected so all good.

4. Run

$ node index.js

and then

$ ls -l

to get

-rw-------  1 morten morten   54 Sep  3 14:28 my-logger.log
-rw-r--r--  1 morten morten   72 Sep  3 14:28 my-logger.log.2020-09-02.gz

Note how the compressed file has "-rw-r--r--" file permisions, and not "-rw-------" as expected. Thus, "mode" config is apparently ignored when "compress" is "true" in the log4js config. (If I set "compress" to "false" then the backup file has the expected "-rw-------" file permissions).

I am using log4js version 6.3.0 (the newest one).