[Bug]: `dotnet workload restore` uniquely emits warning MSB3982: EnableDynamicPlatformResolution ... Platforms not set

### Issue Description

Platform negotiation seems to fail with MSB3982, but only for `dotnet workload restore` commands. Ordinary `dotnet restore` and `dotnet build` produce no such warnings.

### Steps to Reproduce

```
git clone https://github.com/AArnott/Library.Template
cd Library.Template
git checkout bug/traversalPlatforms
cd azure-pipelines
dotnet build # no warnings
dotnet workload restore # senseless warnings
```

### Expected Behavior

No warnings or errors.

### Actual Behavior

Warnings are emitted about needing `Platforms` or `Platform` defined, though they don't make sense, and don't appear for ordinary builds.

> C:\Program Files\dotnet\sdk\8.0.303\Microsoft.Common.CurrentVersion.targets(1716,5): warning MSB3982: EnableDynamicPlatformResolution is true but referenced project 'C:\Users\andarno\source\repos\Library.Template\src\dirs.proj' has no 'Platforms' or 'Platform' metadata set. It will be built without a specified platform.
> C:\Program Files\dotnet\sdk\8.0.303\Microsoft.Common.CurrentVersion.targets(1716,5): warning MSB3982: EnableDynamicPlatformResolution is true but referenced project 'Library\Library.csproj' has no 'Platforms' or 'Platform' metadata set. It will be built without a specified platform.

### Analysis

_No response_

### Versions & Configurations

dotnet --info
.NET SDK:
Version: 8.0.303
Commit: 29ab8e3268
Workload version: 8.0.300-manifests.d7126b9e
MSBuild version: 17.10.4+10fbfbf2e

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\8.0.303\

.NET workloads installed:
[aspire]
Installation Source: SDK 8.0.300, VS 17.12.35126.67, VS 17.12.35125.258
Manifest Version: 8.1.0/8.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.aspire\8.1.0\WorkloadManifest.json
Install Type: Msi

Host:
Version: 8.0.7
Architecture: x64
Commit: 2aade6beb0

.NET SDKs installed:
6.0.132 [C:\Program Files\dotnet\sdk]
6.0.424 [C:\Program Files\dotnet\sdk]
7.0.120 [C:\Program Files\dotnet\sdk]
7.0.203 [C:\Program Files\dotnet\sdk]
7.0.317 [C:\Program Files\dotnet\sdk]
8.0.107 [C:\Program Files\dotnet\sdk]
8.0.206 [C:\Program Files\dotnet\sdk]
8.0.303 [C:\Program Files\dotnet\sdk]
8.0.400-preview.0.24324.5 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.30 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.32 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.30 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.30 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.19 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
C:\Users\andarno\source\repos\Library.Template\global.json

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download