QtMsbuild causes Qt static library's dependencies to call postBuildEvent twice

When building a project via command line using the msbuild command, building a Qt static library project causes all of it's dependencies to rebuild in a such a way the postBuildEvent is triggered twice. This issue does not occur when there is no Qt project.

This problem is exacerbated with the /m flag, especially when projects depend on files copied in the postBuildEvent of a previous project.

For example, a project with a non-Qt static library and a Qt static library where the Qt library depends on the non-Qt library.

When building the order of events:

• Non-Qt Project builds and runs postBuildEvent
• Qt Project determines Non-Qt project needs to be built
• Non-Qt Project determines it is up to date
• Non-Qt Project runs postBuildEvent (second time)
• Qt Project builds

I've attached a sample VS2019 project that showcases the issue.

Calling msbuild QtBugTest.sln /p:Platform=x64;Configuration=Release will build the Qt library that shows the issue.

Calling msbuild QtBugTest.sln /p:Platform=x64;Configuration=NonQtRelease will build two normal static libraries showing this issue does not occur without Qt.