Java in a relative path doesn't work consistently

[peterix]

Java is in MultiMC/jre

java path set to: jre/bin/java:

• Works fine in the settings test
• Doesn't work for launch - binary not found.

java path set to: ../jre/bin/java:

• Doesn't work in the settings test
• Binary is found, but cannot be started:

MultiMC version: 0.4.8---1

Minecraft folder is:
instances/1.7.10/minecraft

Java path is:
../jre/bin/java

Java Arguments:
[-Xms6000m, -Xmx6000m, -Duser.language=en, -jar, /home/peterix/minecraft/build/debug/jars/NewLaunch.jar]

The process failed to start.
Could not launch minecraft!

This is because there's a difference between running java from all those different places.

Also, a second issue:

If you take the flash drive with you, you have a problem, because MultiMC detects that you moved to a different machine and re-detects java there.