The VS generators add a custom command to `CMakeLists.txt` to re-run
CMake when input files have changed. Mark this custom command as if it
were specified with `USES_TERMINAL`. We already do this for the
equivalent `rebuild_cache` target in Makefile and Ninja generators.
This matters since commit d6353e74b4 (VS: Add policy to build custom
commands concurrently, 2023-03-10) because with policy CMP0147 set to
NEW, we now add `BuildInParallel` in `.vcxproj` file entries for custom
commands that do not have `USES_TERMINAL` set, but we do not want to
re-run CMake concurrently with other custom commands.
Issue: #18405
In commit 33c15ae2b9 (VS: Build custom commands concurrently when
possible, 2023-01-19, v3.26.0-rc1~56^2) we added `BuildInParallel` to
custom commands in `.vcxproj` files, but that had to be reverted by
commit abb1c12162 (VS: Revert "Build custom commands concurrently when
possible", 2023-03-07, v3.26.0-rc6~3^2) because some projects may have
custom commands that accidentally rely on serial execution in MSBuild.
Add a policy to use `BuildInParallel` for custom commands in projects
that have been updated to set the policy to `NEW`.
Fixes: #18405
