Refactoring in commit 3882718872 (VS: Decouple solution generation from
`.sln` file format, 2025-09-15) accidentally left out automatic
detection of the external project type id from its file extension.
Since the `Visual Studio 18 2026` generator is new, we can switch
to the `.slnx` file format without changing behavior for users of
VS 2022 and older.
Fixes: #25887
In `cmGlobalVisualStudio7Generator::WriteTargetsToSolution`, we skip
writing `ZERO_CHECK.proj` to solution file as the check in
`cmGlobalVisualStudioGenerator::IsInSolution` returns `false` for
`ZERO_CHECK`. However, we write ZERO_CHECK to ProjectDependencies for
external projects as there are no checks in
`cmGlobalVisualStudio71Generator::WriteExternalProject`.
Similar to `cmGlobalVisualStudioGenerator::IsInSolution`, we introduce
`IsDepInSolution(const std::string&)` which excludes `ZERO_CHECK.proj`
from being added to sln file for the cases where we have `ZERO_CHECK.proj`.
Fixes: #23708
Add "RunCMake.include_external_msproject" test to use the TYPE, GUID, and
PLATFORM options to include_external_msproject. Since projects with
custom types and platforms cannot be loaded without special VS plugins
validate the results by directly parsing the generated solution (.sln).
Co-Author: Leonid Yurchenko <nocturne@qarea.com>
Brad King
Sumit Bhardwaj
Dario Passet
Joerg Bornemann
Beeble