Compiler tweaks for Wasm & WASI

[QuantumSegfault]

• On Wasm, do as Clang does and mangle C main as either __main_void or __main_argc_argv as appropriate
• Don't force use of direct wasm-ld for WASI targets. Allows clang to be set as the link driver (via -gcc).
• Define appropriate versions for the new wasm32-unknown-wasip1, -wasip2, and -wasip3 targets, and account for the fact that the legacy -wasi triple aliases to p1 at the moment.
• Emit musl-style __assert_failed on WASI.

Split from #5152

[QuantumSegfault]

Requesting review

@thewilsonator

[QuantumSegfault]

Should the dmd/mangle/package.d‎ changes be upstreamed instead? It's a little awkward cause it would still be dependent on this PR being merged first (for the isTargetWasm helper).

[thewilsonator]

Should the dmd/mangle/package.d‎ changes be upstreamed instead?

Yes.

[thewilsonator]

FAIL: LDC :: codegen/wasi.d (222 of 397)
******************** TEST 'LDC :: codegen/wasi.d' FAILED ********************
Exit Code: 1
 Command Output (stdout):
--
# RUN: at line 4
/__w/ldc/build/bin/ldc2 -mtriple=wasm32-unknown-wasi -output-ll -output-o -of=/__w/ldc/build/tests/codegen/Output/wasi.d.tmp.wasm /__w/ldc/ldc/tests/codegen/wasi.d
# executed command: /__w/ldc/build/bin/ldc2 -mtriple=wasm32-unknown-wasi -output-ll -output-o -of=/__w/ldc/build/tests/codegen/Output/wasi.d.tmp.wasm /__w/ldc/ldc/tests/codegen/wasi.d
# .---command stderr------------
# | wasm-ld: error: cannot open crt1.o: No such file or directory
# | wasm-ld: error: unable to find library -lc
# | wasm-ld: error: cannot open /usr/lib/llvm21/lib/clang/21/lib/wasm32-unknown-wasi/libclang_rt.builtins.a: No such file or directory
# | clang: error: linker command failed with exit code 1 (use -v to see invocation)
# | Error: /usr/lib/llvm21/bin/clang failed with status: 1
# `-----------------------------
# error: command failed with exit status: 1

on the Alpine Musl targets, not sure why.

[QuantumSegfault]

FAIL: LDC :: codegen/wasi.d (222 of 397)
******************** TEST 'LDC :: codegen/wasi.d' FAILED ********************
Exit Code: 1
 Command Output (stdout):
--
# RUN: at line 4
/__w/ldc/build/bin/ldc2 -mtriple=wasm32-unknown-wasi -output-ll -output-o -of=/__w/ldc/build/tests/codegen/Output/wasi.d.tmp.wasm /__w/ldc/ldc/tests/codegen/wasi.d
# executed command: /__w/ldc/build/bin/ldc2 -mtriple=wasm32-unknown-wasi -output-ll -output-o -of=/__w/ldc/build/tests/codegen/Output/wasi.d.tmp.wasm /__w/ldc/ldc/tests/codegen/wasi.d
# .---command stderr------------
# | wasm-ld: error: cannot open crt1.o: No such file or directory
# | wasm-ld: error: unable to find library -lc
# | wasm-ld: error: cannot open /usr/lib/llvm21/lib/clang/21/lib/wasm32-unknown-wasi/libclang_rt.builtins.a: No such file or directory
# | clang: error: linker command failed with exit code 1 (use -v to see invocation)
# | Error: /usr/lib/llvm21/bin/clang failed with status: 1
# `-----------------------------
# error: command failed with exit status: 1

on the Alpine Musl targets, not sure why.

I guess the WASI test only runs on Alpine musl?

But the reason is now WASI links with clang, not wasm-ld directly, so it's automatically trying to link against libc and the compiler rt (which was exactly my intention for doing so). Problem is system clang isn't WASI enabled (need wasi-sdk's wasm32-wasip2-clang)

Short of introducing wasi-sdk as a dependency into the test-suite, need to keep clang from grabbing system libs

[QuantumSegfault]

Okay. Main mangle upstreamed: dlang/dmd#23303

[QuantumSegfault]

Okay...that should do it.

I don't know what's special about Alpine's build of llvm/clang...

But it should be fixed now. Forced it to use wasm-ld (requesting lld explicitly asks for wasm-ld) instead of default wasm-component-ld (which requires separate install) for WASIp2 target. And also to not try to link in anything from libc, etc. (cause normal distributions don't come with a WASI sysroot).

Eventually we'll want to reevaluate the Wasm/WASI CI situation, but we can do that later.