Move ASDF plugin installation into Cloudflare ENV vars

We have to use the `UNSTABLE_PRE_BUILD` env var in our build process to get the asdf `java` plugin
installed before the build system installs the tool versions defined in our `.tool-versions` file.

I'm wary of using an ENV var labeled "UNSTABLE", as it might disappear without warning, but also
this project has effectively no risk, so I'm going to go with the ease of use it affords us.

build.sh

@@ -1,23 +1,14 @@
 #!/bin/bash
 
-echo "Inspecting asdf plugins"
-asdf info
-asdf plugin list
-
 echo "Beginning build"
 
+# This will auto-succeed in the CI environment, but I've kept it here in case others come to use the
+# script
 echo "installing asdf java plugin"
 asdf plugin add java https://github.com/halcyon/asdf-java.git
 
 echo "Installing local versions"
 asdf install
 
-# echo "Fetching JDK"
-# # Grab the java binary and put it in our path
-# wget https://github.com/adoptium/temurin17-binaries/releases/download/jdk-17.0.8%2B7/OpenJDK17U-jre_x64_linux_hotspot_17.0.8_7.tar.gz
-# # When transform the initial directory name into something static, to make it easier to work with
-# tar --gzip --transform 's,^[^/]+,jdk,x' --extract --file OpenJDK17U-jre_x64_linux_hotspot_17.0.8_7.tar.gz
-# export PATH=$PWD/jdk/bin:$PATH
-
 echo "Building release"
 npx shadow-cljs release :client