Expectation for llvm toolchain with -rtlib=compiler-rt

Compiling this:
```
$ clang -fuse-ld=lld -rtlib=compiler-rt -stdlib=libc++ foo.cpp -o foo
```
generates a binary which is linked against libgcc_s

```
$ ldd foo|grep libgcc_s

	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f104bc66000)
```
Not sure it is expected?
