[mono][wasm] Versioned SupportedOSPlatform filters valid browser P/Invokes #132297

Description

Publishing a browser WebAssembly app that references a net11.0-browser
class library with P/Invokes regressed between .NET 11 preview 6 and
preview 7.

The publish succeeds without a diagnostic in both versions. With preview 7,
the generated pinvoke-table.h silently omits the library's valid browser
P/Invokes. Calling one at runtime then throws
System.EntryPointNotFoundException.

Reproduction

Minimal repository:

https://github.com/Sieluna/dotnet-wasm-pinvoke-platform-repro

dotnet-wasm-pinvoke-platform-repro-main.zip

Run:

bash ./repro.sh

The script installs both exact SDKs and matching wasm-tools workloads,
publishes the same project with isolated Emscripten caches, and checks the
generated tables.

Successful Linux CI run:

https://github.com/Sieluna/dotnet-wasm-pinvoke-platform-repro/actions/runs/31757943237

The run uploads both generated tables in the pinvoke-tables artifact.

Results

Preview 6 generates:

double emscripten_get_now();

static PinvokeImport __Internal_imports[] = {
    {"emscripten_get_now", emscripten_get_now},
};

Preview 7 generates an empty module:

static PinvokeImport __Internal_imports[] = {
};

{"__Internal", __Internal_imports, 0},

The class library is referenced through ProjectReference, so NuGet asset
selection is not involved.

Expected behavior

A versioned platform attribute such as
SupportedOSPlatform("browser1.0") should match the browser target.
The P/Invoke should be included in the generated table.

Root cause analysis

A normal net11.0-browser class library receives these generated assembly
attributes:

TargetPlatform("browser1.0")
SupportedOSPlatform("browser1.0")

The browser WebAssembly SDK passes TargetOS=browser.

PR #131022 added platform filtering to the Mono P/Invoke collector:

#131022

The current collector compares the complete attribute string with
_targetOS using exact equality:

https://github.com/dotnet/runtime/blob/main/src/tasks/WasmAppBuilder/mono/PInvokeCollector.cs

Therefore browser1.0 != browser. Because a
SupportedOSPlatformAttribute is present but no exact target string is
found, the assembly is treated as unsupported and all its P/Invokes are
skipped.

The comparison should use platform-name/version semantics rather than raw
string equality. A regression test using
SupportedOSPlatform("browser1.0") would cover the standard generated
attribute for net11.0-browser libraries.

Workaround

Setting this on the class library changes the generated support attribute to
SupportedOSPlatform("browser") and restores the P/Invoke:

<SupportedOSPlatformVersion>0.0</SupportedOSPlatformVersion>

This should not be required for a standard net11.0-browser class library.

Tested environments

• Windows 11, local publish
• ubuntu-latest, GitHub Actions
• Mono browser WebAssembly backend