The following pre-requisites need to be installed for building the repo:

# Windows (Windows 7+)

1. Install [Visual Studio 2017](https://www.visualstudio.com/en-us/products/visual-studio-community-vs.aspx), including Visual C++ support. Visual Studio 2015 also works.
2. Install [CMake](http://www.cmake.org/download/) 3.8.0 or later. Make sure you add it to the PATH in the setup wizard.
3. (Windows 7 only) Install PowerShell 3.0. It's part of [Windows Management Framework 3.0](http://go.microsoft.com/fwlink/?LinkID=240290). Windows 8 or later comes with the right version inbox.

PowerShell also needs to be available from the PATH environment variable (it's the default). Typically it should be %SYSTEMROOT%\System32\WindowsPowerShell\v1.0\.

# Ubuntu (14.04)

Install basic dependency packages:

First add a new package source to be able to install clang-3.9:
```sh
echo "deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty-3.9 main" | sudo tee /etc/apt/sources.list.d/llvm.list
wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-get update
```

```sh
sudo apt-get install cmake clang-3.9 libicu52 libunwind8 uuid-dev
```

# Mac OSX (10.11.5+)

1. Install [Command Line Tools for XCode 8](https://developer.apple.com/xcode/download/) or higher. 
2. Install [CMake](https://cmake.org/download/). Launch `/Applications/CMake.app/Contents/MacOS/CMake` GUI. Goto "OSX App Menu -> Tools -> Install For Command Line Use" and follow the steps. CMake < 3.6 has [a bug](https://cmake.org/Bug/view.php?id=16064) that can make `--install` fail. Do `sudo mkdir /usr/local/bin` to work around.
3. Install OpenSSL. Build tools have a dependency on OpenSSL. You can use [Homebrew](http://brew.sh/) to install it: with Homebrew installed, run `brew install openssl` followed by `ln -s /usr/local/opt/openssl/lib/libcrypto.1.0.0.dylib /usr/local/lib/`, followed by `ln -s /usr/local/opt/openssl/lib/libssl.1.0.0.dylib /usr/local/lib/`.
4. Install ICU (International Components for Unicode). It can be obtained via [Homebrew](http://brew.sh/): run `brew install icu4c` followed by `brew link --force icu4c` 

# Bash on Ubuntu on Windows (Windows 10 Creators Update or later)

Make sure you run with Ubuntu 16.04 Xenial userland (this is the default after Windows 10 Creators Update, but if you enabled the "Bash on Ubuntu on Windows" feature before the Creators Update, you need to [upgrade manually](https://blogs.msdn.microsoft.com/commandline/2017/04/11/windows-10-creators-update-whats-new-in-bashwsl-windows-console/)). Running `lsb_release -a` will give you the version.

Install basic dependency packages:

First add a new package source to be able to install clang-3.9:
```sh
echo "deb http://llvm.org/apt/xenial/ llvm-toolchain-xenial-3.9 main" | sudo tee /etc/apt/sources.list.d/llvm.list
wget -O - http://llvm.org/apt/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-get update
```

```sh
sudo apt-get install cmake clang-3.9 libunwind8 uuid-dev
```