Fix crash generating closure functions calls with LLVM 11 (#1361)
Fix crash generating closure functions calls with LLVM 11 (#1361)

Generating code for prepare_closure and gen_closure was crashing.
The code now matches the implementation of the removed LLVM function.

Signed-off-by: Brecht Van Lommel <d22bc6bad61129b636affa2511b3ce522cd74bb3@blender.org>
aconty/OpenShadingLanguage,lgritz/OpenShadingLanguage,imageworks/OpenShadingLanguage,imageworks/OpenShadingLanguage,aconty/OpenShadingLanguage,imageworks/OpenShadingLanguage,brechtvl/OpenShadingLanguage,imageworks/OpenShadingLanguage,brechtvl/OpenShadingLanguage,brechtvl/OpenShadingLanguage,brechtvl/OpenShadingLanguage,lgritz/OpenShadingLanguage,lgritz/OpenShadingLanguage,brechtvl/OpenShadingLanguage,aconty/OpenShadingLanguage,lgritz/OpenShadingLanguage,imageworks/OpenShadingLanguage,aconty/OpenShadingLanguage,aconty/OpenShadingLanguage,lgritz/OpenShadingLanguage