WasmBuildTest can exit with negative code. (#108181)

Author: ilonatommy

src/mono/wasm/Wasm.Build.Tests/BrowserRunner.cs

@@ -18,7 +18,7 @@ internal class BrowserRunner : IAsyncDisposable
 {
     private static Regex s_blazorUrlRegex = new Regex("Now listening on: (?<url>https?://.*$)");
     private static Regex s_appHostUrlRegex = new Regex("^App url: (?<url>https?://.*$)");
-    private static Regex s_exitRegex = new Regex("WASM EXIT (?<exitCode>[0-9]+)$");
+    private static Regex s_exitRegex = new Regex("WASM EXIT (?<exitCode>-?[0-9]+)$");
     private static readonly Lazy<string> s_chromePath = new(() =>
     {
         string artifactsBinDir = Path.Combine(Path.GetDirectoryName(typeof(BuildTestBase).Assembly.Location)!, "..", "..", "..", "..");