That is impossible, because Flutter is written in Dart on top of Skia, most Dart 2.0 features have been done to improve that development experience, using any other language means basically a full rewrite.
I know that.... But apparently with all the issues Flutter has, there is a possibility that a full rewrite will be absolutely necessary to rectify them.
cough Well, this article _is_ about a delightful Lispy alternative to Dart that compiles to Dart, yielding a superior language with Genuine Dart Inside(tm) and elegant support of Flutter.
Dart may end up living on inside ClojureDart, much like DOS living on deep inside Windows and PCs.