The server start command resolves symbolic links incorrectly on z/OS 3.1

[jimblye]

The server start command calculates the location of the Liberty installation directly and resolves any symbolic links that might occur in that path. The implementation first tries the "realpath" command, then the "readlink -e" command and finally if neither of those implementations are supported it uses it's own implementation for resolving symbolic links.
z/OS has not supported either of the realpath or readlink commands until z/OS 3.1. Unfortunately, the z/OS implementation of readlink has a bug. So we need to avoid calling readlink on z/OS. We should probably avoid calling realpath as well, in case they suddenly add an implementation of that.

If there is a stack trace, please include the FULL stack trace (without any [internal classes] lines in it). To find the full stack trace, you may need to check in $WLP_OUTPUT_DIR/messages.log

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Expected behavior
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Diagnostic information:

• OpenLiberty Version: [e.g. 21.0.0.8 - 21.0.0.10]
• Affected feature(s) [e.g. mpHealth-3.0]
• Java Version: [i.e. full output of java -version]
• server.xml configuration (WITHOUT sensitive information like passwords)
• If it would be useful, upload the messages.log file found in $WLP_OUTPUT_DIR/messages.log

Additional context
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