Exclude the PIC test on Windows.

The codepath tested there does not get run on Windows.
Merge topic 'INTERFACE_POSITION_INDEPENDENT_CODE' into next

4a62667 Exclude the PIC test on Windows.
Use the QT_INCLUDE_DIR instead of QT_HEADERS_DIR

Perhaps this will fix Qt4Targets test on Mac.
Merge topic 'qt4-target-depends' into next

fa18e4c Use the QT_INCLUDE_DIR instead of QT_HEADERS_DIR
Don't end paths with a slash.

Perhaps this will fix the test with Visual Studio.
Merge topic 'target-includes-defines-commands' into next

aca4916 Don't end paths with a slash.