Hello
That's a well-known problem on Windows... And unfortunately here the problem occurs within the *il2cpp.exe* compiler driver supplied by Unity with their editor. They should have used the -filelist option. e.g. instead of :
% libtool -static -o myStaticLib.a objfile1.obj objfile2.obj objfile3.obj ... objfileN.obj %
the Unity il2cpp compiler driver should do :
% libtool -static -o myStaticLib.a -filelist file_containing_the_list_of_object_files.txt %
I already contacted the person who was in charge of implementing that in il2cpp.exe but got no reply yet. Let's hope it gets fixed quickly. Don't hesitate to forward this problem report to the Unity team because ATM only them can fix that (and if necessary, insist that "building for iOS targets on Windows is not supported" is not an answer. The problem is identified and the solution is known, that fix is a 5 minutes job).
Best regards && happy new year,