JNA UnsatisfiedLinkError triggers "Your current operating system is not supported" banner

Issue Summary

When starting Bitbucket Server 6.9+, regardless of JVM, the following message is logged:

020-03-04 08:29:20,550 WARN  [spring-startup]  c.a.s.i.w.c.NioUnsupportedCondition NIO process execution failed
java.lang.UnsatisfiedLinkError: Failed to create temporary file for /com/sun/jna/linux-x86-64/libjnidispatch.so library: No space left on device
  at com.sun.jna.Native.loadNativeDispatchLibraryFromClasspath(Native.java:1026)
  at com.sun.jna.Native.loadNativeDispatchLibrary(Native.java:988)
  at com.sun.jna.Native.<clinit>(Native.java:195)
  at com.zaxxer.nuprocess.linux.LibEpoll.<clinit>(LibEpoll.java:29)
  at com.zaxxer.nuprocess.linux.LinuxProcess.<clinit>(LinuxProcess.java:44)
  at com.zaxxer.nuprocess.linux.LinProcessFactory.runProcess(LinProcessFactory.java:49)
  at com.zaxxer.nuprocess.NuProcessBuilder.run(NuProcessBuilder.java:273)
  at com.atlassian.stash.internal.web.conditions.NioUnsupportedCondition.runNioProcess(NioUnsupportedCondition.java:79)
  at com.atlassian.stash.internal.web.conditions.NioUnsupportedCondition.<init>(NioUnsupportedCondition.java:33)
  ...

(The stack trace above is for Linux, but a variation of it is also possible on Windows.)

When starting Bitbucket Server, the following message is displayed:

Your current operating system is not supportedAs of Bitbucket 7.0, it will no longer be possible to start the application with an unsupported operating system.

In Bitbucket Server 6.9 and 6.10 this does not interfere with the functionality of the system and can be ignored.

Steps to Reproduce

1. Restrict access to $HOME/.cache for the user running Bitbucket Server, or place it on a full filesystem
2. Start Bitbucket Server

Expected Results

Bitbucket Server starts without issue, no warning is displayed, and the system runs without issue.

Actual Results

The exception shown above is logged, and:

• On 6.9 and 6.10, a banner is displayed indicating the current operating system is unsupported, but otherwise the system works normally
• On 7.0, the system will fail to start and display a message indicating the current operating system is unsupported

Workaround

Add the following to JVM_SUPPORT_RECOMMENDED_ARGS:

• Linux: JVM_SUPPORT_RECOMMENDED_ARGS="-Djna.tmpdir=$BITBUCKET_HOME/tmp"
• Windows: set JVM_SUPPORT_RECOMMENDED_ARGS=-Djna.tmpdir=%BITBUCKET_HOME%\tmp

This will change where the JNA library attempts to unpack its dispatch library so it will be written to Bitbucket Server's home directory instead of the user's home directory.