First of all, it's important to remember that the warnings are (usually) there for a reason. If you can find a way to avoid linking the symbols that the warning refers to, that's a far preferable course of action.
Now... As the question notes, the linker emits the warnings because they're in library sections named '.gnu.warning.*'. And as explained at length in this answer, there's no way to suppress this with a command line switch.
But renaming the relevant sections will suppress the warnings.
(You could try removing the sections, but the __evoke_* symbols are referenced in the relocation tables. Renaming is simpler, and can be reversed in future - although of course you should back up the original of any library you do this to.)
objcopy --rename-section .gnu.warning.<symbol>=.xgnu.warning.<symbol> libX.a libX-nowarnings.aYou can link the modified library, or replace the original in situ. Of course, whether this is possible or advisable depends on your specific circumstances.