SCons: Add a comment I forgot to add in earlier.
SCons: Add a comment I forgot to add in earlier.

This comment was supposed to be added to an earlier change as part of review
feedback, but I accidentally left it out when I pushed. Add it in now.

andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin