CMP0147 seemingly exposes NEW behavior by default in v3.27.0-rel3
Our Visual Studio 17.6.4 solution fails spectacularly, when trying to build from a build system created with CMake 3.27.0-rel3 (but working with the current 3.26.4). At this moment for several reasons (confidential, non-trivial code, ...) I'm not able to pinpoint this and provide a minimal example. I can only say that at least lots of include paths are not known, causing more and more errors.
My first suspect was/is the new parallel build of custom commands for Visual Studio (we create a lot of them programmatically from our own framework of cmake scripts). Reading the documentation, the default behavior of the relevant policy should still be OLD. But there are instances of "BuildInParallel" inside ZERO_CHECK.vcxproj which are not in the one, created from 3.26, without setting the policy deliberately from our side anywhere in any kind.
<CustomBuild Include="C:\Projects\...\CMakeFiles\8fb50d26fc3a48049fbe39b67f06b5d7\generate.stamp.rule">
...
<LinkObjects Condition="'$(Configuration)|$(Platform)'=='RelWithDebInfo|Win32'">false</LinkObjects>
<BuildInParallel Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">true</BuildInParallel>
<Message Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Checking Build System</Message>
...