chore: Fix seed assembly project build failure (#10576)

* chore: fix failed build of seed assembly project

* chore: add exitcode validation for snapshot tests

Author: filzrev

samples/seed/dotnet/assembly/BuildFromAssembly.csproj

@@ -9,11 +9,4 @@
     <NoWarn>CS1591</NoWarn>
   </PropertyGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Microsoft.SourceLink.GitHub">
-      <PrivateAssets>all</PrivateAssets>
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
-    </PackageReference>
-  </ItemGroup>
-
 </Project>

test/docfx.Snapshot.Tests/SamplesTest.cs

@@ -56,6 +56,7 @@ public async Task Seed()
 
         using var process = Process.Start("dotnet", $"build \"{s_samplesDir}/seed/dotnet/assembly/BuildFromAssembly.csproj\"");
         await process.WaitForExitAsync();
+        VerifyExitCode(process);
 
         if (Debugger.IsAttached || IsWslRemoteTest())
         {
@@ -121,7 +122,8 @@ public async Task SeedMarkdown()
         var outputPath = nameof(SeedMarkdown);
         Clean(samplePath);
 
-        Program.Main(["metadata", $"{samplePath}/docfx.json", "--outputFormat", "markdown", "--output", outputPath]);
+        var exitCode = Program.Main(["metadata", $"{samplePath}/docfx.json", "--outputFormat", "markdown", "--output", outputPath]);
+        Assert.Equal(0, exitCode);
 
         await VerifyDirectory(outputPath).AutoVerify(includeBuildServer: false);
     }
@@ -156,10 +158,12 @@ public Task Extensions()
 #if DEBUG
         using var process = Process.Start("dotnet", $"build \"{samplePath}/build\"");
         process.WaitForExit();
+        VerifyExitCode(process);
         Assert.Equal(0, Exec("dotnet", "run --no-build --project build", workingDirectory: samplePath));
 #else
         using var process = Process.Start("dotnet", $"build -c Release \"{samplePath}/build\"");
         process.WaitForExit();
+        VerifyExitCode(process);
         Assert.Equal(0, Exec("dotnet", "run --no-build -c Release --project build", workingDirectory: samplePath));
 #endif
 
@@ -239,4 +243,19 @@ private static bool IsWslRemoteTest([CallerFilePath] string callerFilePath = "")
         return Environment.GetEnvironmentVariable("WSLENV") != null
             && callerFilePath.Contains('\\', StringComparison.Ordinal); // Contains `\` when build on windows environment.
     }
+
+    private static void VerifyExitCode(Process process)
+    {
+        if (!process.HasExited)
+            throw new InvalidOperationException("Process is not exited yet.");
+
+        // Gets exit code before closing process.
+        var exitCode = process.ExitCode;
+
+        // Close process to flush stdout/stderr logs.
+        process.Close();
+
+        // Assert exit code
+        Assert.Equal(0, exitCode);
+    }
 }