[wasm][coreclr] Make run.cmd work with wasm arch

[radekdoulik]

No description provided.

[dotnet-policy-service]

Tagging subscribers to this area: @agocke, @dotnet/runtime-infrastructure
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR enables run.cmd (Windows test runner script) to work correctly with the wasm architecture by fixing platform detection logic. The changes distinguish between the build machine OS (where scripts run) and the target OS (what the tests target), which is essential for cross-compilation scenarios like WASM.

Changes:

• Fixed platform detection in run.py to use sys.platform instead of args.host_os for determining file extensions and script types
• Added wasm architecture support to run.cmd with proper defaults (HostOS=browser, RunWithNodeJS=1)
• Fixed MSBuild condition in tests.targets to use build machine OS instead of target OS for chmod commands

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/tests/run.py	Changed from args.host_os to sys.platform for determining Windows-specific file extensions (.exe, .cmd, .bat) since these depend on the build machine, not target OS
src/tests/run.cmd	Added wasm architecture support with automatic HostOS=browser default and RunWithNodeJS flag, mirroring existing run.sh behavior
src/tests/Common/tests.targets	Changed from TargetOS to OS MSBuild property for chmod condition to properly detect build machine OS

[Copilot]

Pull request overview

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