[native_toolchain_c] Support Clang on Windows

[dcharkes]

Bug: #1892

It seems that both Clang via https://github.com/llvm/llvm-project/releases/tag/llvmorg-19.1.0, and Clang via the MSVC installer come with batteries included and link to the windows headers (added an use of wprintf).

(The Clang-for-Windows on the Dart CI does not come with batteries included: see #1892 (comment).)

Does not add support for arm64 (neither msvc nor clang): #170

[github-actions]

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// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 87.409% (+0.009%) from 87.4%
when pulling 8b2a8a7 on windows-clang
into f179ec2 on main.

[mosuem]

Is this some kind of fuzzy testing?

[dcharkes]

Heh, it would be fuzz testing if we would randomize the params and run it nightly. Now it's a poor mans combination of trying to cover some combination of params 😄

[dcharkes]

Thanks @mkustermann and @mosuem ! 🙏