[backport 11.0] autoexport writes repository resource bundles using system Charset rather than UTF-8

To reproduce:

• Create a new project from the 4.1.0-SNAPSHOT archetype
• Add "<file.encoding>US-ASCII</file.encoding>" to the "systemProperties" section in the main pom
• Build & start the project
• Edit a repository resource bundle through the console, for instance, add a "é"
• This "é" is stored by autoexport as a "?"