WebAssembly: doesn't support emscripten data layout

[kassane]

LDC2 version: 1.38.0
EMCC version: 3.1.59

Based in my analysis kassane/sokol-d#3 (comment).

I've detected conflicts between targets involving only ldc2 + emcc with LTO enabled on both.

wasm-ld: warning: Linking two modules of different target triples: '/home/kassane/.cache/zig/p/122083537ec3463ee4b2d520bf86a36b1057ab05abfe712c32bae1048f9b0c6e2a13/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/lto/libc.a(llrintl.o at 2994444)' is 'wasm32-unknown-emscripten' whereas 'ld-temp.o' is 'wasm32-unknown-unknown-wasm'
wasm-ld: warning: Linking two modules of different data layouts: '/home/kassane/.cache/zig/p/122083537ec3463ee4b2d520bf86a36b1057ab05abfe712c32bae1048f9b0c6e2a13/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten/lto/libc.a(frexpf.o at 1903762)' is 'e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-f128:64-n32:64-S128-ni:1:10:20' whereas 'ld-temp.o' is 'e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20'

emsc-libc:
e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-f128:64-n32:64-S128-ni:1:10:20
ldc:
e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20

and ldc2 no have wasm32-unknown-emscripten triple-target.

[JohanEngelen]

The warning is fixed by #4672

The data layout that I get with LDC master and LLVM15, 17, and 18 is the same as emsc-libc:
e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-f128:64-n32:64-S128-ni:1:10:20