Improve ch0 based on user feedback

book/src/ch0/index.md

@@ -55,6 +55,10 @@ repo](https://github.com/rust-console/gba).
 
 ## Compiling
 
+The next steps only work once you've got some source code to build. If you need
+a quick test, copy the `hello1.rs` file from our examples directory in the
+repository.
+
 Once you've got something to build, you perform the following steps:
 
 * `arm-none-eabi-as crt0.s -o crt0.o`

docs/ch0/index.html

@@ -185,6 +185,9 @@ later on this is where you can put it. You also need to build it into a
 that the GBA has about our program.</li>
 </ul>
 <a class="header" href="#compiling" id="compiling"><h2>Compiling</h2></a>
+<p>The next steps only work once you've got some source code to build. If you need
+a quick test, copy the <code>hello1.rs</code> file from our examples directory in the
+repository.</p>
 <p>Once you've got something to build, you perform the following steps:</p>
 <ul>
 <li>

docs/print.html

@@ -200,6 +200,9 @@ later on this is where you can put it. You also need to build it into a
 that the GBA has about our program.</li>
 </ul>
 <a class="header" href="#compiling" id="compiling"><h2>Compiling</h2></a>
+<p>The next steps only work once you've got some source code to build. If you need
+a quick test, copy the <code>hello1.rs</code> file from our examples directory in the
+repository.</p>
 <p>Once you've got something to build, you perform the following steps:</p>
 <ul>
 <li>