Cross-compiler targeting macOS

[Jacob Carlborg]

# Docker LDC Darwin

I would like to announce a new project I'm working on: 
docker-ldc-darwin [1]. The project consists of a Dockerfile for 
building a Docker image which has all the necessary tools to 
cross-compile D applications targeting macOS x86-64.

## Features

* Uses Apple's ld64 linker so all features that are being used 
when linking on macOS should work. No reliance on custom linkers 
that need to be kept up to date with the system linker
* Ships with the full macOS SDK (for macOS version 10.15.4)
* No reliance on hacks like allowing undefined symbols when 
linking like Zig and Rust does
* Minimal Docker image. Only the exact files that are required to 
run the compiler and linker are included. Not even a shell is 
included
* The Docker image, all tools and resources are fully 
reproducible and automated. No manual steps involved of uploading 
to random cloud storage accounts

The following tools are included:

* dub
* ldc2
* ldmd2
* rdmd
* ld64 (linker)
* clang (C compiler, used for linking)

## Building

### Prerequisites

* [git](https://git-scm.com)
* [Docker](https://www.docker.com)

### Building the Docker Image

Follow the steps below to build the Docker images by running the 
commands in
the terminal:

1. Clone the git repository:
     ```
     git clone 
https://github.com/d-cross-compiler/docker-ldc-darwin && cd 
docker-ldc-darwin
     ```
1. Build the Docker image:
     ```
     docker build -t ldc-x86_64-apple-macos .
     ```

## Usage

By default, the `ldc2` compiler will be invoked.

### Compiling Hello World

Compile Hello World:

```
$ uname
Darwin
$ cat <<EOF > main.d
import std;

void main()
{
     writeln("Hello World");
}
EOF
$ docker run --rm -v "$(pwd):/work" ldc-x86_64-apple-macos main.d
$ ./main
Hello World
```

For more information and examples, see the readme [1].

[1] https://github.com/d-cross-compiler/docker-ldc-darwin

--
/Jacob Carlborg