Package: qt5-qmake
File: /usr/lib/<triplet>/qt5/mkspecs/qmodule.pri
Control: affects -1 + src:qtdeclarative-opensource-src
While building qtdeclarative-opensource-src, I noticed that its build
log contains -fdebug-prefix-map= flags that correspond to a
qtbase-opensource-src build. Apparently those flags leak into
qmodule.pri and get picked up by qtdeclarative-opensource-src. I guess
you want to remove that flag.