pr: Update part of the docs (#17)

* Add cursor rendering section to window manager documentation

* Add cursor scale system commands to syscalls.md

* Add settings documentation for BoredOS

* Document cross-compiler build instructions for Linux

* Create README.md for BoredOS architecture documentation

* Update Architecture Overview link in README

* Reorganize Color Settings section in settings.md

docs/build/toolchain.md

@@ -8,7 +8,7 @@ To build BoredOS, you need the following tools:
 
 1.  **x86_64 ELF GCC Cross-Compiler**:
     -   `x86_64-elf-gcc`: The C compiler targeting the freestanding overarching ELF environment.
-    -   `x86_64-elf-ld`: The linker to combine object files into the final `boredos.elf` kernel binary and userland variables.
+    -   `x86_64-elf-ld`: The linker to combine object files into the final `boredos.elf` kernel and userland binaries.
 
 2.  **NASM**:
     -   Required to compile the `.asm` files in `src/arch/` and `src/userland/crt0.asm`. It formats the output as `elf64` objects to be linked alongside the C code.
@@ -19,3 +19,49 @@ To build BoredOS, you need the following tools:
 
 4.  **QEMU** (Optional but highly recommended for testing):
     -   `qemu-system-x86_64` is used to virtualize the OS for testing or to mess around.
+
+## Building the Cross-Compiler on Linux
+
+### Availability Issue
+
+On most Linux distributions, the `x86_64-elf-gcc` cross-compiler binary is **not pre-packaged** in standard repositories. The only notable exception is **Arch Linux** and Arch-based distributions (Manjaro, EndeavourOS, etc.), where it can be installed via `pacman`:
+
+```bash
+pacman -S x86_64-elf-gcc x86_64-elf-binutils
+```
+
+For all other Linux distributions (Debian, Ubuntu, Fedora, openSUSE, etc.), you **must build the cross-compiler from source**.
+
+### Building from Source
+
+To build the x86_64-ELF GCC cross-compiler:
+
+1.  **Download prerequisites**:
+    -   GNU Binutils source
+    -   GCC source
+
+2.  **Configure and build Binutils**:
+    ```bash
+    ../binutils-*/configure --target=x86_64-elf --prefix=/usr/local/cross
+    make && make install
+    ```
+
+3.  **Configure and build GCC**:
+    ```bash
+    ../gcc-*/configure --target=x86_64-elf --prefix=/usr/local/cross \
+        --without-headers --enable-languages=c
+    make all-gcc && make install-gcc
+    ```
+
+4.  **Add to PATH**:
+    ```bash
+    export PATH="/usr/local/cross/bin:$PATH"
+    ```
+
+Verify the installation:
+
+```bash
+x86_64-elf-gcc --version
+```
+
+> **Note**: Building the cross-compiler can take 20-30 minutes depending on system performance. This is a one-time setup cost.