Revert "Move wiki pages to github pages (#18497)"

This reverts commit 40eb803de1.

docs/_install-and-build/Building-Ethereum.md

@@ -1,22 +0,0 @@
----
-title: Building Ethereum
----
-## Installation Instructions
-
-Follow the appropriate link below to find installation instructions for
-your platform.
-
-* [Installation Instructions for Mac OS X](../doc/Installation-Instructions-for-Mac)
-* [Installation Instructions for Windows](../doc/Installation-instructions-for-Windows)
-* Installation Instructions for Linux/Unix
-  * [Ubuntu](../doc/Installation-Instructions-for-Ubuntu)
-  * [Arch](../doc/Installation-Instructions-for-Arch)
-  * [FreeBSD](../doc/Installation-Instructions-for-FreeBSD)
-* [Setup for Raspberry Pi](https://github.com/ethereum/wiki/wiki/Raspberry-Pi-instructions)
- *  [ARM](../doc/Installation-Instructions-for-ARM)
-* [Usage instructions for Docker](../doc/Running-in-Docker)
-
-## Quick Links
-
-* [Ubuntu PPA](https://launchpad.net/~ethereum/+archive/ubuntu/ethereum)
-* [Download Page](https://geth.ethereum.org/downloads)