Add "Posix" global version conditional for Emscripten targets

[ryuukk]

I just had this thought after seeing this: https://forum.dlang.org/post/odqtqqravqlfcqjgfywo@forum.dlang.org

Haven't tested yet, but i submit the PR otherwise i'll forget

And i can't compile ldc from source:

cmake -G Ninja ../ -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$PWD/../install-ldc

/usr/bin/ld: cannot find -lLLVMSymbolize: No such file or directory

[ryuukk]

I managed to build ldc from source, and i managed to produce a wasm file with that:

./bin/ldc2 -mtriple=wasm32-emscripten-none -L-allow-undefined bin/app.d

import std;


extern(C) void _start()
{
    writeln("hi");
}

I'll try to do the same with druntime and phobos

[JohanEngelen]

is this correct? Musl? that is more than just posix.

[ryuukk]

emscripten uses musl, musl is POSIX compliant

[kinke]

Hmm interesting. Do you have a link to confirm this? I found emscripten-core/emscripten#13006 which seems to support this.

The proper place to add the musl-compatible predefined versions is

ldc/driver/main.cpp

Lines 921 to 923 in dd0ff1e

	case llvm::Triple::Emscripten:
	VersionCondition::addPredefinedGlobalIdent("Emscripten");
	break;

[JohanEngelen]

X86 for sure is wrong

[JohanEngelen]

linux probably also incorrect?

[kinke]

Superseded by #4750.