Find testlib (moved from ../CMakeLists.txt)

--- autotests/CMakeLists.txt.orig	2018-03-15 19:28:26 UTC
+++ autotests/CMakeLists.txt
@@ -1,8 +1,10 @@
 include(ECMAddTests)
 
 if(BUILD_QT4)
+    find_package(Qt4 REQUIRED COMPONENTS QtTest)
     set(TEST_LIB ${QT_QTTEST_LIBRARY})
 else()
+    find_package(Qt5 REQUIRED COMPONENTS Test)
     set(TEST_LIB Qt5::Test)
 endif()
 
