WasmBuildTest can exit with negative code

[ilonatommy]

Before the change:

Error: incorrect localized value for Sunday in locale zh-CN. Expected 'nedeľa' but got 'Sunday'.
WASM EXIT -1
Exception: System.Exception: Timed out after 120s waiting for 'WASM EXIT' message
     at Wasm.Build.Tests.BrowserRunner.WaitForExitMessageAsync(TimeSpan timeout) in /workspaces/runtime/src/mono/wasm/Wasm.Build.Tests/BrowserRunner.cs:line 211
     at Wasm.Build.Tests.WasmTemplateTestsBase.RunBrowser(String config, String projectFile, String language) in /workspaces/runtime/src/mono/wasm/Wasm.Build.Tests/Templates/WasmTemplateTestsBase.cs:line 119
     at Wasm.Build.Tests.WasmTemplateTestsBase.RunBrowser(String config, String projectFile, String language) in /workspaces/runtime/src/mono/wasm/Wasm.Build.Tests/Templates/WasmTemplateTestsBase.cs:line 120
     at Wasm.Build.Tests.IcuTestsBase.BuildAndRunIcuTest(String config, String templateType, Boolean aot, String testedLocales, GlobalizationMode globalizationMode, String extraProperties, Boolean onlyPredefinedCultures, String language, String icuFileName) in /workspaces/runtime/src/mono/wasm/Wasm.Build.Tests/IcuTestsBase.cs:line 180; _testOutput=[] Executing (Captured Output) - /workspaces/runtime/artifacts/bin/dotnet-latest/dotnet new wasmbrowser  -  in pwd /workspaces/runtime/artifacts/bin/Wasm.Build.Tests/Release/net9.0/linux-x64/wbt artifacts/icu_Release_False_0zfc3ohv_13h

After:
Just failure with -1, no timeout exception.

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