An nice advertisement for llvm-gcc.

We know if we add -emit-llvm option to llvm-gcc will deduce emit bc
code, but the problem once llvm-gcc as the linker in some configure
system, it's will call the default ld in default and have no idea to
change this, maybe we can set the default linker as llvm-ld once
-emit-llvm as the option of gcc. And we can't just rename llvm-ld as
ld because. llvm-ld will call binutils ld. So we can make llvm-gcc
more like gcc even if emit-llvm. By the way, llvm-ld can't recognize
the options -pthread, it's an weak to compile some project. Such as
And also we can make the same modification on llvm-g++:) and so on.