Update GettingStarted.md

Author: nicked

docs/HowToGuides/GettingStarted.md

@@ -138,15 +138,7 @@ toolchain as a one-off, there are a couple of differences:
    The required version of Xcode changes frequently and is often a beta release.
    Check this document or the host information on <https://ci.swift.org> for the
    current required version.
-1. **If you are running on Apple Silicon hardware** (M1, M2, etc):
-   Ensure you have the native arm64 build of Python configured.
-   Run `file $(which python3)`; it should print "arm64".
-   If it prints "x86_64", you are running Python in compatibility mode (Rosetta),
-   and will need to ensure the native version of Python is installed and
-   configured in your PATH.
-   Running `uname -m` should also print "arm64", otherwise your terminal is also
-   running in Rosetta mode.
-1. Install [CMake][], [Ninja][] and [Sccache][]:
+2. Install [CMake][], [Ninja][] and [Sccache][]:
    - Via [Homebrew][] (recommended):
      ```sh
      brew install cmake ninja sccache
@@ -204,6 +196,15 @@ toolchain as a one-off, there are a couple of differences:
 * If you installed and want to use Sccache: Run `sccache --version`; check
   that this succeeds.
 
+> **Note**  
+> If you are running on Apple Silicon hardware (M1, M2, etc), ensure you have
+> the native arm64 build of these dependencies installed and configured in your PATH.
+>
+> e.g. running `file $(which python3)` should print "arm64".
+>
+> If it prints "x86_64", you are running Python in compatibility mode (Rosetta), and building Swift will fail.
+> Running `uname -m` should also print "arm64", otherwise your terminal is running in Rosetta mode.
+
 ### The roles of different tools
 
 At this point, it is worthwhile to pause for a moment