This is an Ada compiler, from GCC-13.

Since Ada support must be built by an Ada-capable compiler, only platforms for
which a bootstrap compiler is available can build it.

It is based on release versions of the Free Software Foundation's GNU Compiler
Collection.  It uses the GCC Runtime Library Exception, so the resulting
binaries have no licensing requirements.  Binaries produced by the AUX compiler
should be legally handled the same as binaries produced by any FSF compiler.

It offers continuous improvements to the Ada 2022 standard since GCC 11.