[1501] Change language to say it may cause errors

configure.ac

@@ -1710,7 +1710,7 @@ cat <<EOF
   generated by "make" before "make check" can be run.
 
   When running "make install" do not use any form of parallel or job
-  server options (such as GNU make's -j option). Doing so is guaranteed
-  to cause errors.
+  server options (such as GNU make's -j option). Doing so may cause
+  errors.
 
 EOF

doc/guide/bind10-guide.xml

@@ -837,9 +837,9 @@ as a dependency earlier -->
           <screen>$ <userinput>make install</userinput></screen>
         </para>
         <para>
-          Please note that you should not use any form of parallel or job
-          server options (such as GNU make's -j option) when performing
-          this step. Doing so is guaranteed to cause errors.
+          Please don't use any form of parallel or job server options
+          (such as GNU make's <command>-j</command> option) when
+          performing this step. Doing so may cause errors.
         </para>
         <note>
           <para>The install step may require superuser privileges.</para>