[OE-core] [meta-clang] LLVM shared library support

[Martin Kelly]

Hi,

I noticed that meta-clang builds only static LLVM libraries, unlike the 
meta-oe version of LLVM 3.3, which builds shared libraries. In fact, 
this appears to be the LLVM upstream default as well.

What is the reason for the difference? Shared versions of LLVM would be 
useful for reducing the size of programs linked to it and making smaller 
filesystem images.

Thanks,
Martin