RFR: modified backport of 8265666 -> 8266558: Enable AIX build platform to make external debug symbols

[Andrew Leonard]

Please can I request a review of this backport of the AIX support for
external debug symbols.
This backports the jdk(17) change
https://bugs.openjdk.java.net/browse/JDK-8265666
modified for jdk8u build system:
webrev's : http://cr.openjdk.java.net/~aleonard/8266558/
backport bug: https://bugs.openjdk.java.net/browse/JDK-8266558
I have fully tested this jdk8u change downstream at AdoptOpenJDK.
Thanks
Andrew