I don't know everything about Genode, but it sounds like I can maybe help you. Libdl/dlfcn is part of glibc. You can download the source code here:
https://sourceware.org/git/?p=glibc.git;a=tree;f=dlfcn;h=f7d4dfdce29d99c222176e35d58b3e06a836e414;hb=HEAD Genode includes a dynamic linker, so you could possibly implement the dlfcn functions yourself (if you do so, please share your code), you could see if someone who understands the dynamic linker better could do it, or you could try to find a workaround. Note that Genode's libc does have dlfcn.h, but the default implementation just gives an error message.