C# DLL not updated on rebuild after system time manipulation

### Tested versions

- Reproduciable in v4.5.1.stable.mono.official [f62fdbde1]

### System information

Windows10 - Godot-v4.5.1.stable.mono.official [f62fdbde1]

### Issue description

I've encountered a potential bug in the Godot C# version where modifying the system time can prevent subsequent C# code changes from being reflected in the built DLL.

### Steps to reproduce

1. Have a Godot C# project with some existing C# scripts.
2. Change the system time on your local machine forward (e.g., from 2025-11-18 to 2025-11-20).
3. Make a trivial change to a C# script (e.g., add a comment, modify a variable) and build the project within Godot. Observe that the build succeeds.
4. Change the system time back to its original/correct time.
5. Make another distinct change to the same or a different C# script, for example, print "hello world" in '_Ready'. Build the project again.
6. Start the game in editor, no print showing in output panel.
7. Move to `.godot\mono\temp\bin\Debug` , the dll's last update time is 2025-11-20, not 2025-11-18

### Minimal reproduction project (MRP)

show in steps

Reproduce the issue in a Godot C# project using the system-time changes described, then inspect the build output under .godot\mono\temp\bin\Debug. Compare the generated DLL timestamp and runtime behavior after changing the clock back; done means subsequent C# edits are reflected in the built DLL and the expected output appears.

Written by the indexing model from the issue text.