RFR : 8202322: AIX: symbol visibility flags not support on xlc 12.1

[Baesken, Matthias]

Hello  ,  could you please review this small adjustment to  the symbol visibility compilation settings on AIX ?
Currently  we use  XLC 12.1  to compile  JDK on AIX .

However XLC 12.1   does not support  the "-qvisibility=hidden"  setting currently set on AIX.
It was introduced with  XLC 13.1 . Christoph found some info about it here :

https://www.ibm.com/developerworks/aix/library/au-aix-symbol-visibility-part2/index.html

Setting it  only generates  hundreds  of warnings  in the build log , warnings look like this :
XlC12.1

bash-4.4$ xlC -qversion
IBM XL C/C++ for AIX, V12.1 (5765-J02, 5725-C72)
Version: 12.01.0000.0019

bash-4.4$ xlC -qvisibility=hidden sizeof.c -o sizeof_aixxlc
1506-173 (W) Option visibility=hidden is not valid. Enter xlC for list of valid options.

Compare to XLC13.1

bash-3.00$ xlC -qversion
IBM XL C/C++ for AIX, V13.1 (5725-C72, 5765-J07)
Version: 13.01.0000.0008
bash-3.00$ xlC -qvisibility=default sizeof.c -o sizeof_aixxlc
bash-3.00$ xlC -qvisibility=hidden sizeof.c -o sizeof_aixxlc


So it is better to avoid  setting these flags when using xlc12.1   .
Please review :

Bug :

https://bugs.openjdk.java.net/browse/JDK-8202322

Change :

http://cr.openjdk.java.net/~mbaesken/webrevs/8202322/


Best regards, Matthias