[libc] Add enough stubs to support new LLVM 16 sysroot

time.h and wctype.h had "#error not yet implemented" in them. Now time.h is correct (though the functions
are only declared), and wctype.h exists enough to define its types. Also a dlsym stub was added that just
returns 0.

src/libraries/libc/arch/amd64/libdl.cpp

@@ -4,4 +4,5 @@ extern "C" {
     // we have a real libdl
     int dladdr(const void *, void *) { return 0; }
     int dl_iterate_phdr(void *, void *) { return 0; }
+    int dlsym(void *, const char *) { return 0; }
 }