chore(cpn): update to Qt 5.15.2 and rework application packaging (#4270)

Co-authored-by: raphaelcoeffic <raphael.coeffic@frafos.com>
Co-authored-by: philmoz <phil.a.mitchell@gmail.com>

companion/src/storage/firmwareinterface.cpp

@@ -213,7 +213,7 @@ QString FirmwareInterface::seekString(const QString & string)
 {
   QString result = "";
 
-  int start = flash.indexOf(string);
+  int start = flash.indexOf(string.toUtf8());
   if (start > 0) {
     start += string.length();
     int end = -1;