llvm-ar is symlinked as llvm-ranlib and will act as ranlib when invoked in that mode. llvm-ar since compiler/llvm-project@4f2cfbe supports the -X options, but doesn't seem to accept them when running as llvm-ranlib.
In AIX OS , according to https://www.ibm.com/docs/en/aix/7.2?topic=r-ranlib-command
-X mode Specifies the type of object file ranlib should examine. The mode must be one of the following:
32
Processes only 32-bit object files
64
Processes only 64-bit object files
32_64
Processes both 32-bit and 64-bit object files
The default is to process 32-bit object files (ignore 64-bit objects). The mode can also be set with the OBJECT_MODE environment variable. For example, OBJECT_MODE=64 causes ranlib to process any 64-bit objects and ignore 32-bit objects. The -X flag overrides the OBJECT_MODE variable.