[WASI][Mono] Enable Mono AOT on WASI in runtime-wasm CI leg

[pavelsavara]

Summary

This change enables Mono AOT for the WASI target and fixes the test
infrastructure and test gating that the AOT-trimmed WASI builds need.

The core runtime fix is a single line in the WASI driver that defers eager
assembly loading from AOT images. The remaining changes adapt the build
pipelines, AOT test build flow, and platform-detection / test gating so the
trimmed WASI test legs pass.

Motivation

Mono AOT on WASI previously aborted during startup with:

Runtime critical type System.Runtime.Loader.AssemblyLoadContext not found

On WASI, assemblies are resolved through filesystem probing, which is not yet
available while corlib itself is being set up. Eagerly loading the assemblies
referenced by corlib's AOT image (e.g. System.Security.Claims) during that
early phase falls back to the managed AssemblyLoadContext resolving event,
which needs corlib metadata that isn't initialized yet — a reentrancy that
aborts startup.

Changes

Runtime

• src/mono/wasi/runtime/driver.c — Set
  mono_opt_aot_lazy_assembly_load = 1 in mono_wasm_load_runtime. This loads
  assemblies referenced by AOT images lazily (when actually needed) instead of
  eagerly, avoiding the early-startup reentrancy described above. A comment
  documents the rationale.

Build / test infrastructure

• eng/testing/tests.wasm.targets — Skip importing the
  BrowserWasmApp.targets-based local AOT proxy logic on WASI
  ('$(TargetOS)' != 'wasi'), since WASI uses its own AOT build flow.
• eng/pipelines/extra-platforms/runtime-extra-platforms-wasm.yml —
  • Set RunWasmSamples=false for the WASI smoke and AOT legs.
  • Run smoke-only on the WASI AOT leg (shouldRunSmokeOnly: true).
• eng/pipelines/runtime-wasm.yml — Add excludeOptional: false so the
  WASM-only pipeline runs the WASI legs.

Platform detection & test gating

• PlatformDetection.cs — IsBuiltWithAggressiveTrimming now includes
  IsWasi. WASI apps always build with TrimMode=full, but the non-AOT
  LibraryTests leg did not embed the substitution that flips this flag, so it
  reported false. Using IsWasi (not IsWasm) keeps Browser non-AOT
  untrimmed.
• NumberFormatInfoTests.cs — FullICUPlatform now uses
  !PlatformDetection.IsWasm instead of IsNotBrowser, so the WASI target
  (which also lacks full ICU) is excluded.
• DataContractJsonSerializer.cs / DataContractSerializer.cs — Gate the
  FileStreamSurrogate tests with
  [SkipOnPlatform(TestPlatforms.Wasi, ...)]. /tmp is not preopened in the
  wasmtime --dir . sandbox, so TempFile.Create() cannot create temp files.

Cleanup

• Remove the unused src/mono/sample/wasi/jco sample (Program.cs, csproj,
  main.mjs, package.json, package-lock.json, .npmrc).

[pavelsavara]

/azp run runtime-wasm

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Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

Updates the Mono WASI runtime and WASM CI/test configuration to improve coverage and avoid early startup issues when using AOT on WASI.

Changes:

• Enable lazy loading of assemblies referenced by AOT images during WASI runtime initialization to avoid early-resolution reentrancy.
• Disable the default EventSourceSupport=true setting for WASI in browser/WASM test targets.
• Configure the runtime-wasm pipeline wrapper to include optional jobs by setting excludeOptional: false.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/mono/wasi/runtime/driver.c	Sets mono_opt_aot_lazy_assembly_load during WASI runtime startup (plus adds an extern declaration).
eng/testing/tests.browser.targets	Avoids enabling EventSourceSupport by default when TargetOS is wasi.
eng/pipelines/runtime-wasm.yml	Forces optional wasm jobs on by passing excludeOptional: false into the wasm job template.

[pavelsavara]

/azp run runtime-wasm

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

/azp run runtime-wasm

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Copilot]

Pull request overview

Copilot reviewed 13 out of 14 changed files in this pull request and generated no new comments.

Files not reviewed (1)

• src/mono/sample/wasi/jco/package-lock.json: Language not supported

Comments suppressed due to low confidence (1)

src/mono/wasi/runtime/driver.c:262

• monoeg_g_getenv() can return NULL (see main.c usage), but this code unconditionally passes the result to strcmp(). If DOTNET_SYSTEM_GLOBALIZATION_INVARIANT is unset, this will dereference NULL and crash during runtime initialization.

	char* invariant_globalization = monoeg_g_getenv ("DOTNET_SYSTEM_GLOBALIZATION_INVARIANT");
	if (strcmp(invariant_globalization, "true") != 0 && strcmp(invariant_globalization, "1") != 0)
		load_icu_data();

[pavelsavara]

/azp run runtime-wasm

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Azure Pipelines successfully started running 1 pipeline(s).