Directory.Build.Props is ignored when attempting to determine the TargetFramework of a csproj file

Bug Report

• At what date and time did you most recently experience the problem?

2022-07-20

• Where did you experience the problem? E.g. Azure Web Apps, Azure Functions, Azure Container Registry, or offline use.

using Azure/static-web-apps-deploy@v1

• If your repo is publicly available please share its URL:
  It isn't public yet

• What happened?

Detecting platforms...
Could not detect any platform in the source directory.
Error: Could not detect the language from repo.

• What did you expect or want to happen?

Detecting platforms...
Detected following platforms:
  dotnet: 6.0.6

• How can we reproduce it?
  you can use https://github.com/staticwebdev/blazor-starter/generate and then move <TargetFramework>net6.0</TargetFramework> up to a Directory.Build.props file.

• Do you have log output? Please include between the backticks:

Detecting platforms...
Could not detect any platform in the source directory.
Error: Could not detect the language from repo.

Generate the staticwebdev/blazor-starter repository and move the TargetFramework element into Directory.Build.props, then reproduce the detection failure using Azure/static-web-apps-deploy@v1. Trace the project-platform detection entry point responsible for reading the csproj and compare the result with the expected .NET 6.0 detection output; done means the project is detected when its target framework is defined there.