Executing the launcher with arguments such as:
optirum java -jar Minecraft.jar primusrun java -jar Minecraft.jar
will cause the JVM to crash.
Workaround
Execute the launcher without Nvidia Optimus:
java -jar Minecraft.jar
In the launcher, edit the profile Java Settings (Advanced) Executable to use a script containing:
#!/bin/bash
primusrun java "$@"
See attached file.