systemd: install into versioned directory

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@12031 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter08/systemd.xml

@@ -92,6 +92,7 @@ meson --prefix=/usr                 \
       -Dhomed=false                 \
       -Duserdb=false                \
       -Dman=true                    \
+      -Ddocdir=/usr/share/doc/systemd-&systemd-version; \
       ..</userinput></screen>
 
     <variablelist>