As Phillip Kendall mentioned, you can release your content under multiple licenses, as long as one of those licenses is the Creative Commons Attribution-ShareAlike license. The best place to state this is probably in your profile description. You may not need to necessarily mention the CC-BY-SA, as Stack Exchange's policy automatically releases all contributions under that license. The user MultiplyByZero provides an example of this, with code contributions being released under the Unlicense and text contributions under the Creative Commons Zero.
So you can state in your profile description that you release your posts under a different license or licenses, and others can understand that they can use your posts under either the license(s) you specified or the CC-BY-SA.