duplicate man pages in po directory break the build

When trying to build plasma-sdk from Plasma/5.27 git branch (commit d953e867 at the time of writing), recently added duplicate translations break the build:

CMake Error at /usr/local/kde/lib/cmake/KF5DocTools/KF5DocToolsMacros.cmake:203 (add_custom_target):
  add_custom_target cannot create target
  "po-nl-docs-plasma-sdk-engineexplorer-plasmaengineexplorer-1" because
  another target with the same name already exists.  The existing target is a
  custom target created in source directory
  "/home/ratijas/kde/src/kde/workspace/plasma-sdk".  See documentation for
  policy CMP0002 for more details.
Call Stack (most recent call first):
  /usr/local/kde/lib/cmake/KF5DocTools/KF5DocToolsMacros.cmake:234 (kdoctools_create_manpage)
  CMakeLists.txt:92 (kdoctools_install)


CMake Error at /usr/local/kde/lib/cmake/KF5DocTools/KF5DocToolsMacros.cmake:203 (add_custom_target):
  add_custom_target cannot create target
  "po-nl-docs-plasma-sdk-plasmoidviewer-plasmoidviewer-1" because another
  target with the same name already exists.  The existing target is a custom
  target created in source directory
  "/home/ratijas/kde/src/kde/workspace/plasma-sdk".  See documentation for
  policy CMP0002 for more details.
Call Stack (most recent call first):
  /usr/local/kde/lib/cmake/KF5DocTools/KF5DocToolsMacros.cmake:234 (kdoctools_create_manpage)
  CMakeLists.txt:92 (kdoctools_install)

$ tree po/nl
po/nl
├── cuttlefish_editorplugin.po
├── cuttlefish.po
├── docs
│   ├── plasma-sdk
│   │   ├── engineexplorer
│   │   │   └── man-plasmaengineexplorer.1.docbook
│   │   └── plasmoidviewer
│   │       └── man-plasmoidviewer.1.docbook
│   ├── plasma-sdk_engineexplorer
│   │   └── man-plasmaengineexplorer.1.docbook
│   └── plasma-sdk_plasmoidviewer
│       └── man-plasmoidviewer.1.docbook
├── org.kde.plasma.lookandfeelexplorer.po
├── org.kde.plasma.themeexplorer.po
├── plasmaengineexplorer.po
├── plasma_shell_org.kde.plasmoidviewershell.po
└── plasmoidviewer.po