Update README to remove refs to submodules.

README.md

@@ -5,18 +5,20 @@
 Here are some simple steps to get started:
 
 ```sh
-# If you have not yet cloned the repo:
-git clone --recurse-submodules https://git.zxq5.dev/OsDev/FoundryOS.git
-# If you already cloned the repo:
-git submodule update --init --recursive
-
-cargo build
-# This will build the binaries if required - no need to call cargo build.
+git clone https://git.zxq5.dev/OsDev/FoundryOS.git
 cargo run
 ```
 
+## Running in GDB:
+```sh
+USE_GDB=1 cargo run
+```
+
 ### Build dependencies
 
-* jq: checks whether the app is to be run in debugging mode.
 * libisoburn: creates ISO images to be booted from.
 * qemu: to run the kernel.
+
+Optionally,
+
+* GDB: for debugging the kernel.