Error while building kdepim. Error log suggestions don't work.

[A. F. Cano]

Environment: Debian 10/stable.

The log file says:

CMake Error at /home/afc/kde/qt5/lib/cmake/Qt5/Qt5Config.cmake:28 (find_package):
  Could not find a package configuration file provided by "Qt5WebEngine" with
  any of the following names:

    Qt5WebEngineConfig.cmake
    qt5webengine-config.cmake

  Add the installation prefix of "Qt5WebEngine" to CMAKE_PREFIX_PATH or set
  "Qt5WebEngine_DIR" to a directory containing one of the above files.  If
  "Qt5WebEngine" provides a separate development package or SDK, be sure it
  has been installed.
Call Stack (most recent call first):
  CMakeLists.txt:133 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/afc/kde/build/kdepim/CMakeFiles/CMakeOutput.log".

The qtwebengine5-dev package is installed and supplies
Qt5WebEngineConfig.cmake here:

/usr/lib/x86_64-linux-gnu/cmake/Qt5WebEngine/Qt5WebEngineConfig.cmake

I have run kdesrc-build like this:

Qt5WebEngine_DIR=/usr/lib/x86_64-linux-gnu/cmake/Qt5WebEngine/ ./kdesrc-build --stop-on-failure kdepim

To pass the environment variable to kdesrc-build as instructed in the error
message.  The error still occurs.

I have also tried:

CMAKE_PREFIX_PATH=/usr/lib/x86_64-linux-gnu/cmake/Qt5WebEngine/ ./kdesrc-build --stop-on-failure kdepim

but the error still happens.

The CMakeLists.txt file (in the directory where kdesrc-build is) is only 111
lines long, so the above error (line 133) doesn't make sense.  The only other
files on the system with that name (per locate) are fortran-related (in
/usr/share) and in /usr/share/doc.

I have also added the above path to the CMAKE_PREFIX_PATH in
sample-kde-env-master.sh but that doesn't do it either.

I have never tried to build kde apps from source before, so this might be an
obvious problem to the kde programmer but I don't know what else to try.

Any hints will be greatly appreciated.

PS: I have tried in vain to subscribe to the kdepim-users mailing list but I
never got the confirmation email.  I tried multiple times on the web page,
by sending to kdepim-users-request at kde.org and by writing to kdepim-users-owner.
Every email  seems to have gone to a black hole.  Can someone refer this issue
to the mailing list owner? I had no problem subscribing to this mailing list
for instance, or re-subscribing to kde at kde.org (the old email address stopped
working).

Thanks in advance.

Augustine