devplugin.min.js fails to load, not ES5 compliant

[JanStrauss]

Failed to load plug-in script: SyntaxError: parse error (line 1) at [..]/userdata/plugin/devtools.min.js

minified artifact contains arrow functions

$ curl -sL https://github.com/OpenRCT2/plugin-devtools/releases/download/v1.2/devtools.min.js | grep -o "=>" | wc -l
       5

The logs of the pipeline run have expired but I assume it might be mishoo/UglifyJS#5967. Pinning the version to 3.12.5 seems to work locally:

$ uglifyjs --version
uglify-js 3.12.5
$ uglifyjs --compress --mangle --output out/devtools.min.js -- out/devtools.js
$ grep -o "=>" out/devtools.min.js | wc -l
       0
[..]
$ uglifyjs --version
uglify-js 3.19.3
$ uglifyjs --compress --mangle --output out/devtools.min.js -- out/devtools.js
$ grep -o "=>" out/devtools.min.js | wc -l
       5