diff -ruN flightgear-2018.2.1/CMakeLists.txt my/CMakeLists.txt
--- flightgear-2018.2.1/CMakeLists.txt	2018-06-03 09:47:23.000000000 +0200
+++ my/CMakeLists.txt	2018-06-07 01:09:14.621303443 +0200
@@ -596,4 +596,6 @@
 
 
 # The test suite.
-add_subdirectory(test_suite EXCLUDE_FROM_ALL)
+if(ENABLE_TESTS)
+    add_subdirectory(test_suite EXCLUDE_FROM_ALL)
+endif()