libctf should use libz.so.1, not libz.so
Presently, libctf's decompression routine dlopen(3c)s libz.so. This is incorrect; it, like any dlopen user, makes assumptions about the symbols provided by the library that are specific to the major version. As such, it should be using libz.so.1 rather than relying on the compilation symlink. This is guaranteed to be safe even if a different libz appears in the same address space because it is already correctly using RTLD_LOCAL.