WinRT: Clean up target path for mapping file
WinRT: Clean up target path for mapping file

The target inside the mapping file must not start with a slash. However
one must specify a path value in the deployment rules, otherwise it will
be ignored internally.

Task-number: QTCREATORBUG-13835
Change-Id: Ic44cd6bc8c5fd7d48a3a980de566b492180c77fd
Reviewed-by: Oliver Wolff <bfa2c373f7b4cae624ec1928f54bc38b8cd9f442@theqtcompany.com>

Distrotech/qtcreator,kuba1/qtcreator,kuba1/qtcreator,Distrotech/qtcreator,kuba1/qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,Distrotech/qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,xianian/qt-creator,kuba1/qtcreator,danimo/qt-creator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,kuba1/qtcreator,Distrotech/qtcreator,kuba1/qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,xianian/qt-creator,Distrotech/qtcreator,Distrotech/qtcreator,kuba1/qtcreator,Distrotech/qtcreator,xianian/qt-creator,danimo/qt-creator,danimo/qt-creator,danimo/qt-creator,danimo/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,danimo/qt-creator