[CMake] Add support for WebAssembly target architectures

[kateinoigakukun]

To repair the swift-corelibs-foundation build on WebAssembly, we need to add support for Wasm targets to swift-collections' CMake build system.

Checklist

• I've read the Contribution Guidelines
• My contributions are licensed under the Swift license.
• I've followed the coding style of the rest of the project.
• I've added tests covering all new code paths my change adds to the project (if appropriate).
• I've added benchmarks covering new functionality (if appropriate).
• I've verified that my change does not break any existing tests or introduce unexplained benchmark regressions.
• I've updated the documentation if necessary.

[kateinoigakukun]

@swift-ci test

[lorentey]

Looks good! Did you mean this to target the main branch instead of release/1.1?

[kateinoigakukun]

@lorentey You are right, this should target release/1.1. Thanks!

[lorentey]

@swift-ci test

[kateinoigakukun]

@swift-ci test macOS

[kateinoigakukun]

Hi @lorentey, do we have any chance to release a new 1.1.x tag including this change? We need this change to repair Foundation build on Wasm. Thanks in advance 🙏