Fix option

Author: Bill-hbrhbr

CMakeLists.txt

@@ -15,16 +15,9 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS
 
 if(YSTDLIB_CPP_IS_TOP_LEVEL)
     include(CTest)
+    option(YSTDLIB_CPP_BUILD_TESTING "Build the testing tree for ystdlib-cpp." ON)
 endif()
 
-cmake_dependent_option(
-    YSTDLIB_CPP_BUILD_TESTING
-    "Build the testing tree for ystdlib-cpp."
-    ON
-    "YSTDLIB_CPP_IS_TOP_LEVEL"
-    OFF
-)
-
 cmake_dependent_option(
     YSTDLIB_CPP_ENABLE_TESTS
     "Enable unit tests."