Fix path to private lib dir in update/remove helpers

src/shared/shared.cpp

@@ -747,6 +747,15 @@ bool installDesktopFileAndIcons(const QString& pathToAppImage, bool resolveColli
     const QString installPrefixPath = QFileInfo(ownBinaryDirPath).dir().absolutePath();
     QString privateLibDirPath = installPrefixPath + "/" + PRIVATE_LIBDIR;
 
+    // if there is no such directory like <prefix>/bin/../lib/... or the binary is not found there, there is a chance
+    // the binary is just next to this one (this is the case in the update/remove helpers)
+    // therefore we compare the binary directory path with PRIVATE_LIBDIR
+    if (!QDir(privateLibDirPath).exists()) {
+        if (privateLibDirPath.contains(PRIVATE_LIBDIR)) {
+            privateLibDirPath = ownBinaryDirPath;
+        }
+    }
+
     // the following lines make things work during development: here, the build dir path is inserted instead, which
     // allows for testing with the latest changes
     if (!QDir(privateLibDirPath).exists()) {