cmake: Consider source path with underscores

[HuidaeCho]

This PR fixes locale CMake build when the GRASS source path contains underscores. For example, conda-build creates a temporary build directory using timestamp with an underscore (e.g., .../envs/grass-conda/conda-bld/grass_1741956650154/work/build).

Needs testing on Windows...

[nilason]

Perhaps we can extract the file name here with get_filename_component?

[nilason]

Perhaps we can extract the file name here with get_filename_component?

Here I'm referring to L17, where we only extract the locale.

[HuidaeCho]

Perhaps we can extract the file name here with get_filename_component?

Here I'm referring to L17, where we only extract the locale.

Yes, just extracting filename components early would be ideal.

[nilason]

Something like this might work, replacing L16:

set(_locales)
foreach(_locale ${po_files})
  get_filename_component(_loc ${_locale} NAME)
  list(APPEND _locales ${_loc})
endforeach()

[nilason]

Looks good to me!

(#5426 is a blocker for merging any PR currently.)