[ZIPFLDR] Fix ShellExecute opening a .zip (#6714)

ShellExecute on a .zip file fails because the command in the registry
uses rundll32 that passes in an ANSI string, which is the default for
exported functions without a W suffix.

- This should also fix RAPPS not being able to open downloaded .zip files
- I made it use the full path to Explorer for good measure

Fixes regression introduced by 0.4.15-dev-6343-g bf2cec186c (#5411)

CORE-19506

dll/shellext/zipfldr/zipfldr.cpp

@@ -174,12 +174,17 @@ STDAPI DllUnregisterServer()
 
 EXTERN_C
 BOOL WINAPI
-RouteTheCall(IN HWND hWndOwner, IN HINSTANCE hInstance, IN PCWSTR lpStringArg, IN INT Show)
+RouteTheCallW(IN HWND hWndOwner, IN HINSTANCE hInstance, IN PCWSTR lpStringArg, IN INT Show)
 {
     CStringW path = lpStringArg;
     PathRemoveBlanksW(path.GetBuffer());
     path.ReleaseBuffer();
     path = L"\"" + path + L"\"";
-    ShellExecuteW(NULL, L"open", L"explorer.exe", path.GetString(), NULL, SW_SHOWNORMAL);
+
+    WCHAR app[MAX_PATH];
+    GetWindowsDirectoryW(app, _countof(app));
+    PathAppendW(app, L"explorer.exe");
+
+    ShellExecuteW(NULL, L"open", app, path.GetString(), NULL, Show ? Show : SW_SHOWNORMAL);
     return TRUE;
 }

dll/shellext/zipfldr/zipfldr.spec

@@ -2,4 +2,4 @@
 @ stdcall -private DllGetClassObject(ptr ptr ptr)
 @ stdcall -private DllRegisterServer()
 @ stdcall -private DllUnregisterServer()
-@ stdcall RouteTheCall(ptr ptr wstr long)
+@ stdcall RouteTheCallW(ptr ptr wstr long)