Since I so miserably misspelled packaging - a new thread specific to the issue at hand.
I found a "workaround". In short, xlc does not accept arrays of nested array - the bottom line (best message) is: 1506-995 (S) An aggregate containing a flexible array member cannot be used as a member of a structure or as an array element.
At the core - all the other messages come because this (I shall call it nesting).
For the test-http-auth.c file I have a patch (attached).
make ran for while with no issue, then it started running into several files with this same style of specification - doveadm-dict.c being the first one. I ran "make -i" and I notice several files with this - for xlc - "unaccepted" syntax.
Please look at the patch - what it basically is - and let me know whether you would consider accepting patches in this form (e.g., verify gcc (I assume) will accept it as well). If your answer is yes, I shall proceed with the additional files (learn how your MACROS work!) and send them to you. Again, initially I would just send one, e.g., doveadm-dict.c - to be sure your regular compiler also builds this alternate specification.
Thank you for your consideration!
Michael