New review comment by ahesford on void-packages repository

https://github.com/void-linux/void-packages/pull/36250#discussion_r831239633

Comment:
```suggestion
if _java_bin=$(readlink -e /usr/bin/java); then
	_java_bin="${_java_bin%/bin/java}"
	[ -d "${_java_bin}" ] && export JAVA_HOME="${JAVA_HOME:=${_java_bin}}"
fi
unset _java_bin
```
Using `readlink -e` will not work with busybox `readlink`, but people who wish to replace coreutils can be tasked with modifying the Java profile snippet. It saves us from shenanigans and allows us to short-circuit everything when `/usr/bin/java` doesn't exist.