build: avoid dirty docs on fresh bootstrap

* HACKING: Regenerate.

HACKING

@@ -36,11 +36,12 @@ Then, when you want to post your patches:
   git send-email --cover-letter --no-chain-reply-to --annotate \
                  --to=libvir-list@redhat.com master
 
-(Note that the "git send-email" subcommand is usually not in the main git
-package, but part of a sub-package called "git-email".) For a single patch you
-can omit "--cover-letter", but series of a two or more patches needs a cover
-letter. If you get tired of typing "--to=libvir-list@redhat.com" designation
-you can set it in git config:
+(Note that the "git send-email" subcommand may not be in the main git package
+and using it may require installion of a separate package, for example the
+"git-email" package in Fedora.) For a single patch you can omit
+"--cover-letter", but a series of two or more patches needs a cover letter. If
+you get tired of typing "--to=libvir-list@redhat.com" designation you can set
+it in git config:
 
   git config sendemail.to libvir-list@redhat.com