Problem - can't set environment variables when starting ABCL via Slime

[Andrew Sengul]

Hello, I'm using ABCL through Emacs with Slime and I'm having trouble
setting bash environment variables needed for Maven to work. Here's what
I have in my ~/.emacs file:

(setq slime-lisp-implementations
      '((abcl ("/usr/bin/java" "-jar"
               "/path/to/abcl-bin-1.8.0/abcl.jar"
               "/path/to/abcl-bin-1.8.0/abcl-contrib.jar"
               "-Xmx6g")
              :coding-system utf-8-unix
              :env ("JAVA_HOME=/path/to/jdk-12/"
                    "PATH=/opt/apache-maven-3.8.3/bin:$PATH"))))

Problem is, the $JAVA_HOME and $PATH variables are not set for the ABCL
process despite putting them here. The environment variables do work
with other CL implementations. When I set them in SBCL, for example, I
can run (uiop:run-program "echo $PATH" ...) and see the extension added
to the path. This doesn't work in ABCL, and I need those extra
environment variables set in order for Maven to work.

Does anyone know a way to fix this? It works for other CLs, so I'm
guessing something particular about ABCL is preventing the variables
from being set. Thanks,

Andrew