Fix cmake auto tests failing with cmake 2.8.11

After commit 3eca75de67 the use of
<Module>_EXECUTABLE_COMPILE_FLAGS becomes mandatory for 2.8.11 or older.
Therefore use it in test_use_modules - that's supposed to work with all
cmake versions it seems - and bump test_interface to require 2.8.12.

Change-Id: I7cfb6c6f1e8a97be916d372b9d9148490926693c
Reviewed-by: Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com>
Reviewed-by: Stephen Kelly <steveire@gmail.com>

tests/auto/cmake/CMakeLists.txt

@@ -126,11 +126,8 @@ if (QT_WITH_ANGLE OR (NOT WIN32 AND NOT APPLE AND NOT NO_EGL))
 endif()
 expect_pass(test_opengl_lib)
 
-if (NOT CMAKE_VERSION VERSION_LESS 2.8.11)
-    expect_pass(test_interface)
-endif()
-
 if (NOT CMAKE_VERSION VERSION_LESS 2.8.12)
+    expect_pass(test_interface)
     expect_pass(test_interface_link_libraries)
     expect_pass(test_moc_macro_target)
 endif()

tests/auto/cmake/test_interface/CMakeLists.txt

@@ -1,5 +1,5 @@
 
-cmake_minimum_required(VERSION 2.8.11)
+cmake_minimum_required(VERSION 2.8.12)
 
 project(test_interface)
 

tests/auto/cmake/test_use_modules_function/CMakeLists.txt

@@ -12,5 +12,7 @@ add_executable(three three.cpp)
 
 find_package(Qt5Core)
 
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${Qt5Core_EXECUTABLE_COMPILE_FLAGS}")
+
 qt5_use_modules(two Test)
 qt5_use_modules(three Gui Test)