1 The point of this test if the linker already has a weak definition
2 it does not try to find another copy in an archive
4 There are two case to test:
5 1) both the main .o files and the archive have the same weak symbol (_foo)
6 2) main.o has a weak symbol and the archive has a non-weak symbol (_baz)
7 In both cases the linker should ignore the archive.