[SETUP:REACTOS][SYSSETUP] Fix Shift-F10 cmd.exe invocation.

Pressing Shift-F10 to open cmd.exe when the setup program runs from
a different current directory than System32, now works correctly.

Use the 2nd CreateProcessW() `lpCommandLine` parameter, instead of the
1st parameter `lpApplicationName`, so as to use default path search.
The command-line buffer given to the 2nd-parameter can be temporarily
modified by CreateProcessW(), thus use an on-stack buffer.

https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessw#parameters

base/setup/reactos/reactos.c

@@ -2762,19 +2762,19 @@ HotkeyThread(LPVOID Parameter)
     DPRINT("HotkeyThread start\n");
 
     hotkey = GlobalAddAtomW(L"Setup Shift+F10 Hotkey");
-
     if (!RegisterHotKey(NULL, hotkey, MOD_SHIFT, VK_F10))
         DPRINT1("RegisterHotKey failed with %lu\n", GetLastError());
 
     while (GetMessageW(&msg, NULL, 0, 0))
     {
         if (msg.hwnd == NULL && msg.message == WM_HOTKEY && msg.wParam == hotkey)
         {
+            WCHAR CmdLine[] = L"cmd.exe"; // CreateProcess can modify this buffer.
             STARTUPINFOW si = { sizeof(si) };
             PROCESS_INFORMATION pi;
 
-            if (CreateProcessW(L"cmd.exe",
-                               NULL,
+            if (CreateProcessW(NULL,
+                               CmdLine,
                                NULL,
                                NULL,
                                FALSE,

dll/win32/syssetup/install.c

@@ -1049,19 +1049,19 @@ HotkeyThread(LPVOID Parameter)
     DPRINT("HotkeyThread start\n");
 
     hotkey = GlobalAddAtomW(L"Setup Shift+F10 Hotkey");
-
     if (!RegisterHotKey(NULL, hotkey, MOD_SHIFT, VK_F10))
         DPRINT1("RegisterHotKey failed with %lu\n", GetLastError());
 
-    while (GetMessage(&msg, NULL, 0, 0))
+    while (GetMessageW(&msg, NULL, 0, 0))
     {
         if (msg.hwnd == NULL && msg.message == WM_HOTKEY && msg.wParam == hotkey)
         {
+            WCHAR CmdLine[] = L"cmd.exe"; // CreateProcess can modify this buffer.
             STARTUPINFOW si = { sizeof(si) };
             PROCESS_INFORMATION pi;
 
-            if (CreateProcessW(L"cmd.exe",
-                               NULL,
+            if (CreateProcessW(NULL,
+                               CmdLine,
                                NULL,
                                NULL,
                                FALSE,