website.make: Get some make variables from environment. Fixes debuggability.

website.make: Get some make variables from environment.  Fixes debuggability.

If you have a normal lilypond development setup, ie: ~/vc/lilypond, then
something like this script below will allow you to test the website-only
website build.

    #! /bin/sh

    cp -pv Documentation/lilypond-texi2html.init scripts/build
    cp -pv Documentation/web/server/*.htaccess scripts/build

    TEXI2HTML=$(type -p texi2html)
    LILYPOND=$HOME/vc/lilypond
    #from where to copy?
    #ONLINE_ROOT=$LILYPOND/out-www/online-root
    #DOC=$ONLINE_ROOT/Documentation
    DOC=$LILYPOND/Documentation

    make -f website.make website \
      EXAMPLES=$DOC/web/ly-examples/out-www \
      PICTURES=$DOC/pictures/out-www \
      WEBSITE_ONLY_BUILD=1 \
      TOP_SRC_DIR=$(pwd) \
      TRUSTED_DIR=$(pwd)/scripts/build \
      TEXI2HTML_PROGRAM=$TEXI2HTML