Support WebAssembly target platforms wasm{32,64}-unknown-unknown

[jmillikin]

No description provided.

[fmeum]

This generally looks good to me.

Could you add a test that builds a simple binary for wasm using a transition? Ideally that would also include adding a usage of libclang_rt.

[jmillikin]

Tests added:

• wasm32_strlen_libc which builds a 32-bit .wasm binaries with a libc.a dependency, and transitively requires wasm32-unknown-unknown/libclang_rt.builtins.a.
• wasm64_strlen_nolibc which builds a 64-bit .wasm binary with no libc dependency (since 64-bit WebAssembly is still experimental, and therefore WASI SDK doesn't exist currently).
• wasm32_strlen_nolibc which is the same code as ^^ but 32-bit, so wasm-dis can be used to manually verify the expected difference in ABI.

[fmeum]

Thanks for adding tests! CI is failing now though.

[jmillikin]

CI appears to be failing for infrastructure reasons. I'll try poking at it a bit, but it might require a bit of refactoring to the test scripts.

---

container_test (debian, true):

/root/.cache/[...]: write (No space left on device)

container_test (linux_sysroot, true)

bin/wasm-ld: error while loading shared libraries: libxml2.so.2: cannot open shared object file: No such file or directory

test (macos-latest, latest, false)

ERROR: /Users/runner/work/toolchains_llvm/toolchains_llvm/tests/BUILD.bazel:209:10: Compiling wasm_strlen.c failed: (Exit 1): DUMMY_GCC_TOOL failed: error executing CppCompile command (from target //:wasm_strlen) external/rules_rust/rust/private/dummy_cc_toolchain/DUMMY_GCC_TOOL -MD -MF bazel-out/darwin_arm64-fastbuild-ST-ee9519131230/bin/_objs/wasm_strlen/wasm_strlen.d ... (remaining 18 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
src/main/tools/process-wrapper-legacy.cc:80: "execvp(external/rules_rust/rust/private/dummy_cc_toolchain/DUMMY_GCC_TOOL, ...)": No such file or directory

[jmillikin]

Updated tests so that WebAssembly targets get their own directory, and the test script runs bazel clean --expunge before trying to build them -- this is intended as a mitigation to avoid running out of disk space.

Also updated tests/WORKSPACE to match tests/MODULE.bazel, and verified non-bzlmod via the following commands on my local workstation (Linux, Ubuntu 20.04)

bazel-7.0.0 test --enable_bzlmod=false //wasm:all
bazel-7.0.0 test --enable_bzlmod=true //wasm:all
bazel-7.3.2 test --enable_bzlmod=false //wasm:all
bazel-7.3.2 test --enable_bzlmod=true //wasm:all

[jmillikin]

More test updates:

• Added libxml2 to the apt-get setup lines in the Debian-based containers.
• Removed -Wl,-v from the linker options for Wasm tests to work around a bug in wasm-ld, and filed wasm-ld -v exits without generating output llvm/llvm-project#112836 for upstream.

[fmeum]

Thanks, this is a great addition!