[SYCL] Limit the directories that are searched when loading plugins

Currently the default search order is used when loading dependencies of the
plugins (these depencies include the Level Zero loader and the ICD
loader) and that list includes current directory and some other
directories which are not considered safe. This patch limits the list of
directories when loading the dependencies of the plugins.
See: https://learn.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-loadlibraryexa
for reference.

sycl/pi_win_proxy_loader/pi_win_proxy_loader.cpp

@@ -134,11 +134,22 @@ void preloadLibraries() {
   MapT &dllMap = getDllMap();
 
   auto ocl_path = LibSYCLDir / __SYCL_OPENCL_PLUGIN_NAME;
-  dllMap.emplace(ocl_path,
-                 LoadLibraryEx(ocl_path.wstring().c_str(), NULL, NULL));
-
+  // When searching for dependencies of the OpenCL plugin (which includes ICD
+  // loader) limit the list of directories to %windows%\system32 and the
+  // directory that contains the loaded DLL (OpenCL plugin). ICD loader is
+  // located in the same directory as OpenCL plugin. Standard library
+  // dependencies are in the system directory.
+  dllMap.emplace(ocl_path, LoadLibraryEx(ocl_path.wstring().c_str(), NULL,
+                                         LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR |
+                                             LOAD_LIBRARY_SEARCH_SYSTEM32));
+
+  // When searching for dependencies of the Level Zero plugin (which includes
+  // level zero loader) limit the list of directories to %windows%\system32.
+  // In this case we know that the Level Zero Loader is located in the system
+  // directory. Standard library dependencies are in the system directory.
   auto l0_path = LibSYCLDir / __SYCL_LEVEL_ZERO_PLUGIN_NAME;
-  dllMap.emplace(l0_path, LoadLibraryEx(l0_path.wstring().c_str(), NULL, NULL));
+  dllMap.emplace(l0_path, LoadLibraryEx(l0_path.wstring().c_str(), NULL,
+                                        LOAD_LIBRARY_SEARCH_SYSTEM32));
 
   auto cuda_path = LibSYCLDir / __SYCL_CUDA_PLUGIN_NAME;
   dllMap.emplace(cuda_path,