Tests: Don't hang when running Qt5Autogen built with GCC 5 (#15570).

Since Qt 5.4.2, it is necessary to compile against Qt 5 with -fPIC
and not -fPIE when using GCC 5.  Not doing so results in a hanging
test in this case, so use the PIC flag directly instead.

Tests/QtAutogen/CMakeLists.txt

@@ -34,8 +34,8 @@ else()
   include_directories(${Qt5Widgets_INCLUDE_DIRS})
   set(QT_LIBRARIES Qt5::Widgets)
 
-  if(Qt5_POSITION_INDEPENDENT_CODE)
-    set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+  if(Qt5_POSITION_INDEPENDENT_CODE AND CMAKE_CXX_COMPILE_OPTIONS_PIC)
+    add_definitions(${CMAKE_CXX_COMPILE_OPTIONS_PIC})
   endif()
 
   macro(qtx_wrap_cpp)