Well, - and I know that might not be very helpful - the compiler has an option to just generate the .s files and no binaries.
As you wrote that the .s files compile, you just found your workaround.

It may be just a case of adapting a linker script.
At least you should be able to prevent generation of binaries and then compile the .s files.
I am not familiar with the default warp linker, but it can also be a case of the proper -k option to pass to the linker.