compiling.html.in: Kill useless spaces in <pre/>

The <pre/> section is rendered as-is on the page. That is, if all
the lines are prefixed with 4 spaces the rendered page will also
have them. Problem is if we put a box around such <pre/> because
the content might not fix into it.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

docs/compiling.html.in

@@ -13,9 +13,9 @@
     </p>
 
     <pre>
-      $ xz -c libvirt-x.x.x.tar.xz | tar xvf -
-      $ cd libvirt-x.x.x
-      $ ./configure</pre>
+$ xz -c libvirt-x.x.x.tar.xz | tar xvf -
+$ cd libvirt-x.x.x
+$ ./configure</pre>
 
     <p>
       The <i>configure</i> script can be given options to change its default
@@ -28,7 +28,7 @@
     </p>
 
     <pre>
-      $ ./configure <i>--help</i></pre>
+$ ./configure <i>--help</i></pre>
 
     <p>
       When you have determined which options you want to use (if any),
@@ -49,9 +49,9 @@
     </p>
 
     <pre>
-      $ ./configure <i>[possible options]</i>
-      $ make
-      $ <b>sudo</b> <i>make install</i></pre>
+$ ./configure <i>[possible options]</i>
+$ make
+$ <b>sudo</b> <i>make install</i></pre>
 
     <p>
       At this point you <b>may</b> have to run ldconfig or a similar utility
@@ -91,7 +91,7 @@
       drive or manual download, and run this any time libvirt.git
       updates the commit stored in the .gnulib submodule:</p>
     <pre>
-      $ GNULIB_SRCDIR=/path/to/gnulib ./autogen.sh --no-git
+$ GNULIB_SRCDIR=/path/to/gnulib ./autogen.sh --no-git
     </pre>
 
     <p>To build &amp; install libvirt to your home
@@ -99,9 +99,9 @@
     </p>
 
     <pre>
-      $ ./autogen.sh --prefix=$HOME/usr
-      $ make
-      $ <b>sudo</b> make install</pre>
+$ ./autogen.sh --prefix=$HOME/usr
+$ make
+$ <b>sudo</b> make install</pre>
 
     <p>
       Be aware though, that binaries built with a custom prefix will not
@@ -111,8 +111,8 @@
     </p>
 
     <pre>
-      $ ./autogen.sh --system
-      $ make
+$ ./autogen.sh --system
+$ make
     </pre>
 
     <p>
@@ -123,9 +123,9 @@
     </p>
 
     <pre>
-      $ su -
-      # service libvirtd stop  (or systemctl stop libvirtd.service)
-      # /home/to/your/checkout/daemon/libvirtd
+$ su -
+# service libvirtd stop  (or systemctl stop libvirtd.service)
+# /home/to/your/checkout/daemon/libvirtd
     </pre>
 
     <p>
@@ -134,7 +134,7 @@
     </p>
 
     <pre>
-      $ ./run ./tools/virsh ....
+$ ./run ./tools/virsh ....
     </pre>
   </body>
 </html>