Allow tests to be ignored (#12)

CMakeLists.txt

@@ -5,18 +5,21 @@ project(tracelogging)
 include(GNUInstallDirs)
 
 add_compile_options(-Wall -Wextra -Werror)
+set(TRACELOGGING_BUILD_TESTS ON CACHE BOOL "Build tests.")
 
 # Include source
 add_subdirectory(src)
 
 # Only include testing stuff if we are the top level
-if (${CMAKE_PROJECT_NAME} STREQUAL ${PROJECT_NAME})
-    enable_testing()
+if(TRACELOGGING_BUILD_TESTS)
+    if (${CMAKE_PROJECT_NAME} STREQUAL ${PROJECT_NAME})
+        enable_testing()
 
-    if (NOT TARGET Catch2::Catch2)
-        list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/external/Catch2/contrib")
-        add_subdirectory(external/Catch2)
+        if (NOT TARGET Catch2::Catch2)
+            list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/external/Catch2/contrib")
+            add_subdirectory(external/Catch2)
+        endif ()
+
+        add_subdirectory(test)
     endif ()
-
-    add_subdirectory(test)
 endif ()