Fix symbolic link bug of `installDirectory`

[vision57]

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if installDirectory is placed in a path which contains symbolic link, an exception will throw because getCanonicalPath() may resolve to another different path. For example, set installDirectory to ${java.io.tmpdir}/nodejs in mac os x throws exception, because getCanonicalPath() resolve /var/folders/**/nodejs to /private/var/folders/**/nodejs.

Summary

Tests and Documentation