I am not sure why that happens -- libgcc.a wasn't explicitly
asked for; but it stands to reason that one shouldn't specify
No, but it's required for anything that uses the C compiler (which in this case would be glibc and any foreign libraries) --- it contains the implementation of things like (long long) support on 32-bit platforms, exception unwinding, and other compiler intrinsics. You may not use them but glibc does.