CLJS-1130: :foreign-libs regression under Closure optimized builds
CLJS-1130: :foreign-libs regression under Closure optimized builds

:foreign-libs support regressed, we never want to emit a goog.require
for a foreign lib in any other optimization setting other than :none

make the comment string clear on this point to avoid future simple
errors like this one.

mstang/clojurescript,mstang/clojurescript,mstang/clojurescript