[libcalamares] Handle qlonglong when writing YAML

- Handle qlonglong explicitly
- Add a fallbackfor things that convert to qulonglong, to
  avoid these remaining integer types from hitting the
  very end of the if-chain, and being written out as
  the **string** "<typename>"

src/libcalamares/utils/Yaml.cpp

@@ -260,10 +260,20 @@ dumpYamlElement( QFile& f, const QVariant& value, int indent )
     {
         f.write( QString::number( value.toInt() ).toUtf8() );
     }
+    else if ( value.type() == QVariant::Type::LongLong )
+    {
+        f.write( QString::number( value.toLongLong() ).toUtf8() );
+    }
     else if ( value.type() == QVariant::Type::Double )
     {
         f.write( QString::number( value.toDouble() ).toUtf8() );
     }
+    else if ( value.canConvert( QVariant::Type::ULongLong ) )
+    {
+        // This one needs to be *after* bool, int, double to avoid this branch
+        // .. grabbing those convertible types un-necessarily.
+        f.write( QString::number( value.toULongLong() ).toUtf8() );
+    }
     else if ( value.type() == QVariant::Type::List )
     {
         int c = 0;