build.bat cannot build Debug

How to reproduce :

• get w10 Virtual machine as per the build instructions in README, MSVC 2019, all the build dependencies
• make sure Release builds fine : BUILD_INSTALLER=0 USE_CODE_SIGNING=0 UPLOAD_BUILD=0 ./build.bat Release
• run $ BUILD_INSTALLER=0 USE_CODE_SIGNING=0 UPLOAD_BUILD=0 ./build.bat Debug

outcome :

C:\Program Files (x86)\Windows Kits\10\Include\10.0.18362.0\ucrt\stdio.h(2100): message : see declaration of '_scprintf' [C:\Nextcloud\client-building\qtkeychain\build\testclient.vcxproj]
  testclient.vcxproj -> C:\Nextcloud\client-building\qtkeychain\build\Debug\testclient.exe
  Building Custom Rule C:/Nextcloud/client-building/qtkeychain/CMakeLists.txt
  -- Install configuration: "Debug"
  -- Installing: C:/Qt/5.12.9/msvc2017_64/translations/qtkeychain_de.qm
  -- Installing: C:/Qt/5.12.9/msvc2017_64/translations/qtkeychain_fr.qm
  -- Installing: C:/Qt/5.12.9/msvc2017_64/translations/qtkeychain_ro.qm
  -- Installing: C:/Qt/5.12.9/msvc2017_64/translations/qtkeychain_ru.qm
  -- Installing: C:/Qt/5.12.9/msvc2017_64/translations/qtkeychain_zh.qm
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/include/qt5keychain/keychain.h
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/include/qt5keychain/qkeychain_export.h
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/lib/qt5keychaind.lib
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/bin/qt5keychaind.dll
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/mkspecs/modules/qt_Qt5Keychain.pri
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/lib/cmake/Qt5Keychain/Qt5KeychainLibraryDepends.cmake
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/lib/cmake/Qt5Keychain/Qt5KeychainLibraryDepends-debug.cmake
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/lib/cmake/Qt5Keychain/Qt5KeychainConfig.cmake
  -- Installing: C:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/lib/cmake/Qt5Keychain/Qt5KeychainConfigVersion.cmake
"* Copy qt5keychain.dll to c:/Qt/5.12.9/msvc2017_64/bin/ for windeployqt to find it."
/usr/bin/cp: cannot stat 'c:/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/bin/qt5keychain.dll': No such file or directory
"*** Build FAILED: qtkeychain Debug Win64 (single-build-qtkeychain.bat)"
"***** Build FAILED (build.bat)"

 /c/Nextcloud/client-building/libs/Debug/qtkeychain/Win64/bin (master)
$ ls
qt5keychaind.dll

File is not named properly and build script fails to copy it.

Start with build.bat and single-build-qtkeychain.bat, then reproduce the Debug build using the commands and Windows environment in the issue. Trace the install output and the copy step for the Debug Win64 DLL; done means the script copies the produced library successfully and the Debug build completes.