Build broken...again!

SPlatten

I'm using:

Qt Creator 4.14.2
Based on Qt 5.15.2 (Clang 11.0 (Apple), 64 bit)
Built on Mar 19 2021 09:03:22

The other day there was an Xcode update.

Xcode, Version 12.5 (12E262)

My OS:

macOS Big Sur
Version 11.3

Today the application that was running now seems broken completely. I've tried clean then Rebuild, in the Issues all I see is:

*** ^. Stop.
/Users/sy/Qt/Qt/5.15.2/clang_64/mkspecs/features/sdk.mk

It won't build at all, what is going on?

[Edit] Today there was another update for the OS, now version 11.3.1, hasn't helped the Qt issue tho.

[Edit2] This is a copy from the Application Output from clean, then rebuild:

3:18:36: Running steps for project XMLMPAM...
13:18:36: Starting: "/usr/bin/make" clean -j8
The platform SDK has been changed from version 11.1 to version 11.3.
This requires a fresh build. Please wipe the build directory completely,
including any .qmake.stash and .qmake.cache files generated by qmake.
/Users/sy/Qt/5.15.2/clang_64/mkspecs/features/mac/sdk.mk:22: *** ^.  Stop.
13:18:36: The process "/usr/bin/make" exited with code 2.
13:18:36: Starting: "/Users/sy/Qt/5.15.2/clang_64/bin/qmake" /Users/sy/XMLMPAM/XMLMPAM.pro -spec macx-clang CONFIG+=debug CONFIG+=x86_64 CONFIG-=qml_debug CONFIG-=qtquickcompiler
13:18:36: The process "/Users/sy/Qt/5.15.2/clang_64/bin/qmake" exited normally.
13:18:36: Starting: "/usr/bin/make" -f /Users/sy/XMLMPAM/build-XMLMPAM-Desktop_Qt_5_15_2_clang_64bit-Debug/Makefile qmake_all
The platform SDK has been changed from version 11.1 to version 11.3.
This requires a fresh build. Please wipe the build directory completely,
including any .qmake.stash and .qmake.cache files generated by qmake.
/Users/sy/Qt/5.15.2/clang_64/mkspecs/features/mac/sdk.mk:22: *** ^.  Stop.
13:18:36: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project XMLMPAM (kit: Desktop Qt 5.15.2 clang 64bit)
When executing step "qmake"
13:18:36: Elapsed time: 00:01.

Can someone please explain why this is now so broken?

SPlatten

Finally, in the end after a lot of messing around I completely deleted the build folder and then re-created it.

NOTE, at first I emptied the contents of the folder with:

rm -R *

This wasn't enough, I had to go to the parent folder and remote the build folder:

rm -R build-XMLMPAM-Desktop_Qt_5_15_2_clang_64bit-Debug

Then recreate the folder using the Projects/Build area in Qt Creator. Rebuild without problem.