gtkmm3: Allow it to be built without doxygen.

git-svn-id: svn://svn.linuxfromscratch.org/BLFS/trunk/BOOK@24029 af4574ff-66df-0310-9fd7-8a98e5e911e0

x/lib/gtkmm3.xml

@@ -101,7 +101,7 @@
 cd    gtkmm3-build &&
 
 meson --prefix=/usr \
-      -Dbuild-documentation=true &&
+      ..           &&
 
 ninja</userinput></screen>
 
@@ -115,8 +115,29 @@ ninja</userinput></screen>
       Now, as the <systemitem class="username">root</systemitem> user:
     </para>
 
-<screen role="root"><userinput>ninja install &amp;&amp;
-mv -v /usr/share/doc/gtkmm-3.0 /usr/share/doc/gtkmm-&gtkmm3-version;</userinput></screen>
+<screen role="root"><userinput>ninja install</userinput></screen>
+
+    <para>
+      If you have built the documentation (see Command Explanations below) it
+      was installed to <filename
+      class="directory">/usr/share/doc/gtkmm-3.0</filename>. For consistency,
+      move it to a versioned directory as the <systemitem
+      class="username">root</systemitem> user:
+    </para>
+
+<screen role="nodump">mv -v /usr/share/doc/gtkmm-3.0 /usr/share/doc/gtkmm-&gtkmm3-version;</screen>
+
+  </sect2>
+
+  <sect2 role="commands">
+    <title>Command Explanations</title>
+
+    <para>
+      <option>-Dbuild-documentation=true</option>: If you have installed
+      <xref linkend="doxygen"/> this define will build and install the
+      documentation.
+    </para>
+
   </sect2>
 
   <sect2 role="content">
@@ -138,7 +159,7 @@ mv -v /usr/share/doc/gtkmm-3.0 /usr/share/doc/gtkmm-&gtkmm3-version;</userinput>
           /usr/include/gdkmm-3.0,
           /usr/include/gtkmm-3.0,
           /usr/lib/gdkmm-3.0,
-          /usr/lib/gtkmm-3.0, and
+          /usr/lib/gtkmm-3.0, and optionally
           /usr/share/{devhelp/books/gtkmm-3.0,doc/gtkmm-&gtkmm3-version;}
         </seg>
       </seglistitem>