SUMMARY
There is no qtwebkt 5.13, but kdewebkit wants exactly that version.
https://github.com/qtwebkit/qtwebkit/releases

STEPS TO REPRODUCE
1. Install latest tag of qtwebkit
2. Try to build kdewebkit 5.66

OBSERVED RESULT
Full log: https://git.io/JvtOi

CMake Error at /usr/local/Cellar/cmake/3.16.2/share/cmake/Modules/CMakeFindDependencyMacro.cmake:47 (find_package):
  Found package configuration file:

    /usr/local/lib/cmake/Qt5WebKit/Qt5WebKitConfig.cmake

  but it set Qt5WebKit_FOUND to FALSE so package "Qt5WebKit" is considered to
  be NOT FOUND.  Reason given by package:

  Qt5WebKit could not be found because dependency is required to have exact
  version 5.13.x

EXPECTED RESULT
It should work with the latest tag of qtwebkit.

SOFTWARE/OS VERSIONS

macOS: 10.15.3 beta (19D62e)
KDE Plasma Version: N/A
KDE Frameworks Version: 5.66
Qt Version: 5.14

ADDITIONAL INFORMATION
It worked fine in previous release, 5.65