Link libdl (-ldl) to compile ut correctly

ut failed to link correctly because libLLVMSupport (-lLLVMSupport) had undefined references to dlopen, etc.
Fix an error in an earlier refactor attempt, which broke the bindgen.

The earlier refactor (8bc7f223014301d1e82ae80ae0910879d16c8802) removed hard-coded block comments from clay-bindgen. I made a seemingly innocent (albeit naive) change: `return str("...")` -> `return "..."` and this essentially broke clay-bindgen for quite a while, I'm embarrassed to admit. clay-bindgen should build correctly now.