qbs single precompiled header for multiple subprojects

Question

i want use single precompiled header for multiple subprojects.

If i add to project

FileTagger {
  patterns: "/absolute/path/to/header.h"
  fileTags: ["cpp_pch_src"]
}

then pch is not generated. If i add header.h to directory of each subproject then this works:

FileTagger {
  patterns: "header.h"
  fileTags: ["cpp_pch_src"]
}

But of course pch is generated one time for each sub project. So how can i generate pch only one time and use it in multiple subprojects?