Add property FileBasedProgram (#49861)

Author: jjonescz

documentation/general/dotnet-run-file.md

@@ -45,6 +45,8 @@ Additionally, the implicit project file has the following customizations:
     string? directoryPath = AppContext.GetData("EntryPointFileDirectoryPath") as string;
     ```
 
+  - `FileBasedProgram` property is set to `true` and can be used by SDK targets to detect file-based apps.
+
 ## Grow up
 
 When file-based programs reach an inflection point where build customizations in a project file are needed,

src/Cli/dotnet/Commands/Run/VirtualProjectBuildingCommand.cs

@@ -652,6 +652,7 @@ public static void WriteProjectFile(
                     <IncludeProjectNameInArtifactsPaths>false</IncludeProjectNameInArtifactsPaths>
                     <ArtifactsPath>{EscapeValue(artifactsPath)}</ArtifactsPath>
                     <PublishDir>artifacts/$(MSBuildProjectName)</PublishDir>
+                    <FileBasedProgram>true</FileBasedProgram>
                   </PropertyGroup>
 
                   <ItemGroup>

test/dotnet.Tests/CommandTests/Run/RunFileTests.cs

@@ -1856,6 +1856,7 @@ public void Api()
                         <IncludeProjectNameInArtifactsPaths>false</IncludeProjectNameInArtifactsPaths>
                         <ArtifactsPath>/artifacts</ArtifactsPath>
                         <PublishDir>artifacts/$(MSBuildProjectName)</PublishDir>
+                        <FileBasedProgram>true</FileBasedProgram>
                       </PropertyGroup>
 
                       <ItemGroup>
@@ -1935,6 +1936,7 @@ public void Api_Diagnostic_01()
                         <IncludeProjectNameInArtifactsPaths>false</IncludeProjectNameInArtifactsPaths>
                         <ArtifactsPath>/artifacts</ArtifactsPath>
                         <PublishDir>artifacts/$(MSBuildProjectName)</PublishDir>
+                        <FileBasedProgram>true</FileBasedProgram>
                       </PropertyGroup>
 
                       <ItemGroup>
@@ -2007,6 +2009,7 @@ public void Api_Diagnostic_02()
                         <IncludeProjectNameInArtifactsPaths>false</IncludeProjectNameInArtifactsPaths>
                         <ArtifactsPath>/artifacts</ArtifactsPath>
                         <PublishDir>artifacts/$(MSBuildProjectName)</PublishDir>
+                        <FileBasedProgram>true</FileBasedProgram>
                       </PropertyGroup>
 
                       <ItemGroup>