Enable the skip list corpus tests by default

driver_skip_list checks SkipList.cpp against ReferenceImpl, but its tests
were disabled, so the implementation diverged from the documented API
without anything noticing. The corpus tests pass in Debug and Release
builds, so run them like the other implementations' tests.

CMakeLists.txt

@@ -224,13 +224,11 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR AND BUILD_TESTING)
   target_compile_options(driver_skip_list PRIVATE ${TEST_FLAGS})
   target_link_libraries(driver_skip_list PRIVATE skip_list)
 
-  # enable to test skip list
-  if(0)
+  # skip list tests, which cross-check SkipList.cpp against ReferenceImpl
   foreach(TEST ${CORPUS_TESTS})
     get_filename_component(hash ${TEST} NAME)
     add_test(NAME skip_list_${hash} COMMAND driver_skip_list ${TEST})
   endforeach()
-  endif()
 
   # ad hoc testing
   add_executable(conflict_set_main ConflictSet.cpp)