VS: Restore support for PCH in CXX but not C within once target
Fix logic from !5395 (merged) to explicitly disable PCH on sources that should not use the target-wide PCH rules.
Fixes: #21827 (closed)
Backport: release
Fix logic from !5395 (merged) to explicitly disable PCH on sources that should not use the target-wide PCH rules.
Fixes: #21827 (closed)
Backport: release