RFR(xs, jdk10, aix-only): 8171504: [aix] On AIX, -XXaltjvm=<path> option is ignored

[Thomas Stüfe]

Hi all,

may I please have reviews for this small change. It adapts the -XXaltjvm
handling to match all other platforms.

(Note that this patch has not the intention of improving the code, I almost
verbatim copied the code from linux. Improvements were done in different
changes, see e.g. JDK-8171508 ("os::jvm_path -XXaltjvm processing error
after 8066474") and JDK-8173828 ("realpath is unsafe").
Issue: https://bugs.openjdk.java.net/browse/JDK-8171504

Webrev:
http://cr.openjdk.java.net/~stuefe/webrevs/8171504-aix-xxaltjvm-path-is-ignored/webrev.00/webrev/

Thank you!

Kind Regards, Thomas