Support setting custom aptoptions for FAI

/dev/pts might not be available, for for example when running grml-live
inside a (unprivileged) docker container. Then apt/aptitude invocations
cause the following error message to show up:

| E: Can not write log (Is /dev/pts mounted?) - posix_openpt (19: No such device)

Sadly FAI's task_instsoft include the following hardcoded check:

| grep -E "^E:" $LOGDIR/software.log && task_error 472

So whenever the /dev/pts error message shows up, FAI considers this as
error and we're failing installation.

apt supports usage of `-o Dpkg::Use-Pty=0` though to not trigger the
pty related code (pkgDPkgPM::StartPtyMagic()).

By setting the environment variable aptoptions="-o Dpkg::Use-Pty=0" for
FAI execution, we can avoid this error message showing up in FAI's
software.log and being considered as error.

Support passing custom environment variables to the fai command line via
$FAI_ENV.

diff --git a/grml-live b/grml-live
index 8b0adfe..87995df 100755 (executable)
--- a/grml-live
+++ b/grml-live
@@ -756,8 +756,8 @@ else
       mount --bind "${OUTPUT}/grml_sources/" "${CHROOT_OUTPUT}/grml-live/sources/"
 
       log "Executed FAI command line:"
-      log "BUILD_ONLY=$BUILD_ONLY BOOTSTRAP_ONLY=$BOOTSTRAP_ONLY GRML_LIVE_CONFIG=$CONFIGDUMP WAYBACK_DATE=$WAYBACK_DATE fai $VERBOSE -C $GRML_FAI_CONFIG -s file:///$GRML_FAI_CONFIG/config -c$CLASSES -u $HOSTNAME $FAI_ACTION $CHROOT_OUTPUT $FAI_ARGS"
-      BUILD_ONLY="$BUILD_ONLY" BOOTSTRAP_ONLY="$BOOTSTRAP_ONLY" GRML_LIVE_CONFIG="$CONFIGDUMP" fai $VERBOSE \
+      log "$FAI_ENV BUILD_ONLY=$BUILD_ONLY BOOTSTRAP_ONLY=$BOOTSTRAP_ONLY GRML_LIVE_CONFIG=$CONFIGDUMP WAYBACK_DATE=$WAYBACK_DATE fai $VERBOSE -C $GRML_FAI_CONFIG -s file:///$GRML_FAI_CONFIG/config -c$CLASSES -u $HOSTNAME $FAI_ACTION $CHROOT_OUTPUT $FAI_ARGS"
+      $FAI_ENV BUILD_ONLY="$BUILD_ONLY" BOOTSTRAP_ONLY="$BOOTSTRAP_ONLY" GRML_LIVE_CONFIG="$CONFIGDUMP" fai $VERBOSE \
                   -C "$GRML_FAI_CONFIG" -s "file:///$GRML_FAI_CONFIG/config" -c"$CLASSES" \
                   -u "$HOSTNAME" "$FAI_ACTION" "$CHROOT_OUTPUT" $FAI_ARGS | tee -a $LOGFILE
       RC="$PIPESTATUS" # notice: bash-only