Add instructions for building without X11/Wayland

INSTALL.md

@@ -36,7 +36,7 @@ Please refer to the [Dependencies](#dependencies) section.
  16. [Windows](#windows)
  17. [Other](#other)
 2. [Building](#building)
- 1. [Linux/Windows](#linux--windows)
+ 1. [Linux/Windows/BSD](#linux--windows--bsd)
  2. [macOS](#macos)
 3. [Post Build](#post-build)
  1. [Terminfo](#terminfo)
@@ -236,12 +236,23 @@ filling in this section of the README.
 
 ## Building
 
-### Linux / Windows
+### Linux / Windows / BSD
 
 ```sh
 cargo build --release
 ```
 
+On Linux/BSD, if it is desired to build Alacritty without support for either the
+X11 or Wayland rendering backend the following commands can be used.
+
+```sh
+# Force support for only Wayland
+cargo build --release --no-default-features --features=wayland
+
+# Force support for only X11
+cargo build --release --no-default-features --features=x11
+```
+
 If all goes well, this should place a binary at `target/release/alacritty`.
 
 ### macOS