How to create XML files in UTF-8?

It seems that windows always produces UTF-16LE files, but I need it to produce in UTF-8.

Example code I've already tried:

PBDOM_Document xml_doc
PBDOM_ProcessingInstruction xml_process
PBDOM_Element xml_root
constant string root_name = "root_node"

try
	xml_doc = create PBDOM_Document
	xml_doc.newdocument(root_name)
	
	xml_process = create PBDOM_ProcessingInstruction
	xml_process.setname("xml")
	xml_process.setvalue("version", "1.0")
	xml_process.setvalue("encoding", "utf-8")
	// it seems that windows always produce utf16 files
	
	xml_doc.addcontent(xml_process)
	destroy xml_process
	
	xml_root = xml_doc.getrootelement()
	
	// (....)
	
	xml_doc.savedocument("foobar.xml")
	destroy xml_root
	destroy xml_doc

CATCH ( PBDOM_Exception pbde )
	MessageBox( "PBDOM Exception",pbde.getMessage() )
CATCH ( PBXRuntimeError re )
	MessageBox( "PBNI Exception",re.getMessage() )
end try

I use Powerbuilder 2021 Build 1311

;) grateful