More verbose doc build

[Joseph Rushton Wakeling]

Hello all,

The building of the various manuals takes quite a long time, but the build 
process itself is silent so it's not easy to tell if they're actually 
progressing or have somehow hung.

e.g. currently I'm just seeing:

LILYPOND_VERSION=2.17.29 /usr/bin/python -tt ../scripts/lilypond-book.py -I . -I 
./out-www -I /home/joseph/code/lily/pond/Documentation/snippets/out -I 
/home/joseph/code/lily/pond/Documentation/included -I 
/home/joseph/code/lily/pond/Documentation/pictures -I 
/home/joseph/code/lily/pond/Documentation -I 
/home/joseph/code/lily/pond/input/regression 
--process='/home/joseph/code/lily/pond/out/bin/lilypond -dbackend=eps 
--formats=ps,png,pdf  -dinclude-eps-fonts -dgs-load-fonts --header=doctitle 
--header=doctitlecs --header=doctitlede --header=doctitlees --header=doctitlefr 
--header=doctitlehu --header=doctitleit --header=doctitleja --header=doctitlenl 
--header=doctitlezh --header=texidoc --header=texidoccs --header=texidocde 
--header=texidoces --header=texidocfr --header=texidochu --header=texidocit 
--header=texidocja --header=texidocnl --header=texidoczh -dcheck-internal-types 
-ddump-signatures -danti-alias-factor=2' --output=./out-www --format=texi-html 
--loglevel=WARN --info-images-dir=lilypond --lily-output-dir 
/home/joseph/code/lily/pond/out/lybook-db --redirect-lilypond-output learning.tely

... and no change, despite the fact that top reveals various changes of 
different tools being called.

Is there a way to get slightly more verbose output?

Thanks & best wishes,

    -- Joe