RFR 8054817: File ccache only recognizes Linux and Solaris defaults

[Wang Weijun]

Please review the fix at

   http://cr.openjdk.java.net/~weijun/8054817/webrev.00

since we have a new getuid() now for all Unix systems.

It does return -1 on Windows, but I keep the osname.startsWith("Windows") check to be exactly consistent with the current behavior. getuid() might return something not -1 one day on Windows.

Thanks
Max