On AIX, we cannot run on the primordial thread for a number of reasons. (See JDK-8171505). This was asserted for in os::Aix::query_stack_dimensions; however, that is a bad place for this assert, as it is used when printing the native callstack. It was also unnecessary, as we also already assert this in os::init(), which is the right place to assert this.

A lot of work went into making the native callstack as robust as possible, so it should not make any asserts it does not really need.