Add FAQ item for UnsatisfiedLinkError (mount options for /tmp)

[joschi]

On some systems, the /tmp directory has insufficient/wrong mount options causing errors similar to the following:

Caused by: java.lang.UnsatisfiedLinkError: /tmp/jna--1712433994/jna7387046629130767794.tmp: /tmp/jna--1712433994/jna7387046629130767794.tmp: failed to map segment from shared object: Operation not permitted

The KB article https://support.cloudbees.com/hc/en-us/articles/215281717-Jenkins-fails-to-start-with-JNA-error describes how to fix this.