RFR: 8220634: SymLinkArchiveTest should handle not being able to create symlinks

[Liam Miller-Cushon]

This change fixes SymLinkArchiveTest to be consistent with the guidance
from
https://mail.openjdk.java.net/pipermail/compiler-dev/2019-March/013031.html.

bug: https://bugs.openjdk.java.net/browse/JDK-8220634
webrev: http://cr.openjdk.java.net/~cushon/8220634/webrev.00/
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