compiler: add support for panic_debug with -cg

vlib/v/parser/struct.v

@@ -286,6 +286,7 @@ fn (mut p Parser) interface_decl() ast.InterfaceDecl {
 		mut method := ast.FnDecl{
 			name: name
 			args: args
+			file: p.file_name
 			return_type: table.void_type
 		}
 		if p.tok.kind.is_start_of_type() && p.tok.line_nr == line_nr {