FAQ/Doc updates (#1966)

## Issue Addressed

N/A

## Proposed Changes

Adding a few FAQ's, updating some formatting


Co-authored-by: realbigsean <seananderson33@gmail.com>

book/src/installation-source.md

@@ -15,6 +15,17 @@ Instructions](#detailed-instructions) below. If you have further issues, see
 [Troubleshooting](#troubleshooting). If you'd prefer to use Docker, see the
 [Docker Guide](./docker.md).
 
+## Updating lighthouse
+
+You can update Lighthouse to a specific version by running the commands below. The `lighthouse`
+directory will be the location you cloned Lighthouse to during the installation process.
+`${VERSION}` will be the version you wish to build in the format `vX.X.X`.
+
+- `cd lighthouse`
+- `git fetch`
+- `git checkout ${VERSION}`
+- `make`
+
 ## Detailed Instructions
 
 1. Install Rust and Cargo with [rustup](https://rustup.rs/).
@@ -72,4 +83,10 @@ See ["Configuring the `PATH` environment variable"
 
 Make sure you are running the latest version of Rust. If you have installed Rust using rustup, simply type `$ rustup update`.
 
+If compilation fails with `(signal: 9, SIGKILL: kill)`, this could mean your machine ran out of
+memory during compilation. If you are on a resource-constrained device you can
+look into [cross compilation](./cross-compiling.md).
+
+If compilation fails with `error: linking with cc failed: exit code: 1`, try running `cargo clean`.
+
 [WSL]: https://docs.microsoft.com/en-us/windows/wsl/about