You can have files with different rights anywhere on your system. One thing you can do is nuke that build folder then use chown and chmod on the content of your download folder and ensure that everything belongs to the correct user and with read/write properties.

@SGaist Thanks for the suggestion. Sorry for the very delayed reply. I tried few options as in the mentioned link. Adding the qrc path in the application's pro file worked. Thank you!!

@jsulm I meant to change some configurations, if there are some, and fasten the compilation. So if I choose the external resources step, is it feasible to do the following steps: Can I integrate the rcc command that I have to execute manually in terminal, somehow to the make step of the application, so that it is executed automatically? If I achieve the upper step, can I detect, whether the qrc was changed a new rcc compilation is necessary?

@supaiku_ you call that necroposting? This is necroposting! I just discovered resources_big via this thread and it is a-maz-ing. It's also now documented: https://doc.qt.io/archives/qt-5.15/qtcore-cmake-qt5-add-big-resources.html I have a chunky-but-not-altogether-unexpected ~40MB referenced in my qrc, and it was blowing up with the dreaded "virtual memory exhausted: Cannot allocate memory" when compiling on a 32-bit target. No amount of exhaustive and exhausting memory tuning could prevent memory usage (not even involving swap!) from hitting the 2GB critical limit. I simply removed my qrc file from set(PROJECT_SOURCES in CMakeLists and reinstated it in qt5_add_big_resources(PROJECT_SOURCES instead. And boom, compilation blasted through the rcc step and barely broke 1GB usage getting the whole job done.

@alex_malyu I re-read and you are right. I was sure that only the main expansion file was downloaded and that the patch file download had to be initiated by the app, but this is not the case. At least for now a work around is using two files, but I might get the same problem when the app expands. I am using Windows 7 64-bit and have tried MinGW 4.9.2 compiler on Qt 5.5, MinGW 4.9 on Qt 5.4.2 and MinGW 4.8 on 5.3. I also tried MSVC2012 on Qt 5.5. I will try post a bug report and see if someone can reproduce the same.