Use UTF-8 to decode logs on Java 18 or newer

Signed-off-by: TheKodeToad <TheKodeToad@proton.me>

launcher/java/JavaVersion.h

@@ -25,7 +25,7 @@ class JavaVersion {
     bool operator>(const JavaVersion& rhs);
 
     bool requiresPermGen() const;
-
+    bool defaultsToUtf8() const;
     bool isModular() const;
 
     QString toString() const;