[wasm] build `WasmAppHost` with `UseAppHost=false`

[radical]

WasmAppHost is included in the WebAssembly.Sdk pack, and doesn't have a platform specific package.
Since, this is being built for x64, the build defaults to using the app host, which means that we get a single binary file that can be run directly. But this also means that the binary included in the WebAssembly.Sdk platform-agnostic package will target the platform where it was built.

Instead, build with UseAppHost=false, and update the wasm host to use the managed assembly instead.

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Issue Details

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WasmAppHost is included in the WebAssembly.Sdk pack, and doesn't have a platform specific package.
Since, this is being built for x64, the build defaults to using the app host, which means that we get a single binary file that can be run directly. But this also means that the binary included in the WebAssembly.Sdk platform-agnostic package will target the platform where it was built.

Instead, build with UseAppHost=false, and update the wasm host to use the managed assembly instead.

Author:	radical
Assignees:	radical
Labels:	arch-wasm, area-Build-mono
Milestone:	-