Wrong default filename for --lib --emit-llvm -S

[brson]

x86_64-unknown-linux-gnu/stage1/bin/rustc ../src/test/run-pass/hello.rs --emit-llvm -S --lib

Outputs a file named ../src/test/run-pass/hello. instead of ../src/test/run-pass/hello.ll. It does contain llasm as expected.

[jdm]

Fixed by ea1e360 .