Add a note about build-essential being distro-specific and sometime…

…s installed by `rustup`.

README.md

@@ -13,8 +13,9 @@ page](https://github.com/AstroTechies/astro_modloader/releases/latest), below th
 
 Pre-built binaries are not yet dsitributed for Linux. To build the modloader yourself on Linux:
 
-- Use your distribution's package manager to install `rustup`, `git`, and `build-essential`,
+- Use your distribution's package manager to install `rustup`, and `git`
 - Use `rustup` to install the Rust programming language,
+- If `rustup` doesn't install it for you, install `build-essential` or your distro's equivalent,
 - Use `cargo` to install `cargo-about`,
 - Use `git` to clone the modloader's repository,
 - Then run the following commands in the root of the repository: