Tests: Fix Qt*Autogen.GlobalAutogenTarget to use matching generator

Build the GAT project with the same generator as the rest of the test.
This was accidentally left out of commit 8c8731b422 (Autogen: Add test
for CMAKE_GLOBAL_AUTOGEN/RCC_TARGET, 2018-11-11, v3.14.0-rc1~396^2~2).

Tests/QtAutogen/GlobalAutogenTarget/CMakeLists.txt

@@ -69,6 +69,9 @@ file(MAKE_DIRECTORY ${GAT_BDIR})
 message("___ Configuring GAT project ___")
 execute_process(
     COMMAND "${CMAKE_COMMAND}" "${GAT_SDIR}"
+        -G "${CMAKE_GENERATOR}"
+        -A "${CMAKE_GENERATOR_PLATFORM}"
+        -T "${CMAKE_GENERATOR_TOOLSET}"
         "-DQT_TEST_VERSION=${QT_TEST_VERSION}"
         "-DCMAKE_AUTOGEN_VERBOSE=${CMAKE_AUTOGEN_VERBOSE}"
         "-DQT_QMAKE_EXECUTABLE:FILEPATH=${QT_QMAKE_EXECUTABLE}"