Add prerequisite page

Author: skade

src/SUMMARY.md

@@ -9,6 +9,7 @@
     - [Getting Started](./getting-started.md)
     - [About the compiler team](./compiler-team.md)
     - [How to Build and Run the Compiler](./building/how-to-build-and-run.md)
+        - [Prerequisites](./building/prerequisites.md)
         - [Suggested Workflows](./building/suggested.md)
         - [Bootstrapping](./building/bootstrapping.md)
         - [Distribution artifacts](./building/build-install-distribution-artifacts.md)

src/building/prerequisites.md

@@ -1,3 +1,29 @@
 # Prerequisites
 
-** Coming Soon: https://github.com/rust-lang/rustc-dev-guide/pull/723 **
+Before building the compiler, you need the following things installed:
+
+* Python
+* A C/C++ compiler toolchain
+* cmake
+* rustc
+
+## `rustc` and toolchain installation
+
+Follow the installation given in the [Rust book](https://doc.rust-lang.org/book/ch01-01-installation.html) to install a working `rustc` and the necessary C/++ toolchain on your platform.
+
+## Platform specific instructions
+
+### Windows
+
+* Install [winget](https://github.com/microsoft/winget-cli)
+
+Run the following in a terminal:
+
+```
+winget install python
+winget install cmake
+```
+
+If any of those is installed already, winget will detect it.
+
+Edit your systems `PATH` variable and add: `C:\Program Files\CMake\bin`.