Build failure when the default charset of the JVM is not UTF-8

[lsq27]

Bug description
Tests fail when Charset.defaultCharset().name() doesn't return UTF-8.

Environment
OpenJDK 17.0.7
Windows 11 22H2 language Chinese default charset GBK

Steps to reproduce
Run .\mvnw verify in Windows (default charset GBK).

output:

[INFO]
[INFO] Results:
[INFO]
[ERROR] Failures:
[ERROR]   FlatFileItemWriterBuilderTests.testFlags:282->validateBuilderFlags:462 expected: <GBK> but was: <UTF-8>
[ERROR]   JsonFileItemWriterBuilderTests.testJsonFileItemWriterCreationDefaultEncoding:135->validateBuilderFlags:146 expected: <GBK> but was: <UTF-8>
[INFO]
[ERROR] Tests run: 1552, Failures: 2, Errors: 0, Skipped: 35

Expected behavior
All tests will be passed with different default charset of JVM.