Fixes https://github.com/nomic-ai/gpt4all/issues/1760 LLModel ERROR: Could not find CPU LLaMA implementation.

Inspired by Microsoft docs for LoadLibraryExA (https://learn.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-loadlibraryexa).
When using LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR, the lpFileName parameter must specify a fully qualified path, also it needs to be backslashes (\), not forward slashes (/).

gpt4all-backend/llmodel.cpp

@@ -104,7 +104,7 @@ const std::vector<LLModel::Implementation> &LLModel::Implementation::implementat
 
                     // Add to list if model implementation
                     try {
-                        Dlhandle dl(p.string());
+                        Dlhandle dl(std::filesystem::absolute(p).string());
                         if (!Implementation::isImplementation(dl)) {
                             continue;
                         }