wrong sourcing of build.sh with a local live-build branch

[Luigi Capriotti]

$ lsb_release -rd
Description: Ubuntu 13.10
Release: 13.10

$ apt-cache policy live-build
live-build:
  Installed: 3.0~a57-1ubuntu9
  Candidate: 3.0~a57-1ubuntu9
  Version table:
 *** 3.0~a57-1ubuntu9 0
        500 http://it.archive.ubuntu.com/ubuntu/ saucy/main i386 Packages
        100 /var/lib/dpkg/status

Most live-build scripts include the following line:

( . "${LIVE_BUILD}/scripts/build.sh" > /dev/null 2>&1 || true ) || . /usr/lib/live/build.sh

but that line fails to source build.sh and all the functions file from the local live-build branch hence builds stop with a syntax error when evaluating "Echo".

That line on upstream repo is instead implemented with:

[ -e "${LIVE_BUILD}/scripts/build.sh" ] && . "${LIVE_BUILD}/scripts/build.sh" || . /usr/lib/live/build.sh

which works correctly in both cases.