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

--- autotests/CMakeLists.txt.orig	2020-10-23 16:11:34 UTC
+++ autotests/CMakeLists.txt
@@ -1,4 +1,10 @@
 include(ECMAddTests)
+if(BUILD_QT4)
+    find_package(Qt4 REQUIRED COMPONENTS QtTest)
+else()
+    find_package(Qt5 REQUIRED COMPONENTS Test)
+endif()
+
 set(TEST_LIB
     alkimia
     alkimia-internal