ci(windows): only generate hash for files in prepare-deploy.ps1

[rami3l]

There is a loophole that has been exposed by #5070 when switching to short-circuiting pwsh for all powershell/pwsh scripts, as suggested by @ChrisDenton in #5070 (comment).

Originally, the filtering logic for *.sha256 generation in prepare-deploy.ps1 didn't consider the fact that only files can be hashed. However, since the hashing of directories (which always fails) was silently skipped, the issue never became a CI error until today.

This patch fixes that by mirroring prepare-deploy.bash's find ... -type f more closely so that we only generate hashes for files.

cc @Cloud0310 for review.

[rami3l]

Fix verified by the before/after comparison from:

Before

Run .\ci\prepare-deploy.ps1


    Directory: D:\a\rustup\rustup\dist


Mode                 LastWriteTime         Length Name                                                                 
----                 -------------         ------ ----                                                                 
d-----         9/10/2026  11:13 AM                x86_64-pc-windows-msvc                                               


    Directory: D:\a\rustup\rustup\dist\x86_64-pc-windows-msvc


Mode                 LastWriteTime         Length Name                                                                 
----                 -------------         ------ ----                                                                 
-a----         9/10/2026  11:13 AM       12339712 rustup-init.exe                                                      
-a----         9/10/2026  11:13 AM             65 rustup-init.exe.sha256                                               
-a----         9/10/2026  11:13 AM       12339712 rustup-setup.exe                                                     
-a----         9/10/2026  11:13 AM             65 rustup-setup.exe.sha256                                              

https://github.com/rust-lang/rustup/actions/runs/34469571059/job/102846049919

After

Run .\ci\prepare-deploy.ps1

    Directory: D:\a\rustup\rustup\dist

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d----           9/12/2026  8:06 AM                x86_64-pc-windows-msvc

    Directory: D:\a\rustup\rustup\dist\x86_64-pc-windows-msvc

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a---           9/12/2026  8:06 AM       12339712 rustup-init.exe
-a---           9/12/2026  8:06 AM             65 rustup-init.exe.sha256
-a---           9/12/2026  8:06 AM       12339712 rustup-setup.exe
-a---           9/12/2026  8:06 AM             65 rustup-setup.exe.sha256

https://github.com/rust-lang/rustup/actions/runs/34682121072/job/103522556812?pr=5072

[Cloud0310]

LGTM

[ChrisDenton]

Thanks for following up on this!