[DiscontentDino]

Summary

Add WASI build support.

Changes

• Add extra_lib_dirs and extra_libs to the Artifacts struct for WASI link items.
• Panic when enable_codegen is true for any WASM target.
• Remove unnecessary vec![] macro.
• Set cpp_stdlib to None when using wasi.
• Set extra_lib_dirs to include $WASI_SYSROOT/lib/<triple>/eh (exception handling) and $WASI_SYSROOT/lib/<triple> (WASI libraries) when using WASI.
• Set extra_libs to include c++, c++abi, unwind, and wasi-emulated-process-clocks (c is linked only when the target is wasm32-unknown-unknown).
• Add extra_lib_dirs to the library search paths.
• Link extra_libs in addition to Luau's libs.
• Disable the codegen compilation setting for any WASM target in testcrate.
• Disable codegen function declarations and calls for WASM targets in testcrate.
• Document WASI requirements and initialization for wasm32-unknown-unknown.