Fix DESTDIR/PREFIX logic

Hopefully this is now according to GNU standards.

src/include/deploy.sh

     esac
 }
 
-check_env() {
-    #
-    # Check that critical variables are set correctly
-    #
-    test -n "$destdir" || die "could not determine DESTDIR"
-    test -d "$destdir" || die "DESTDIR: no such directory: $destdir"
-}
-
 deploy_item() {
     #
     # Deploy item and make it look like wanted
     fi
 }
 
-get_destdir() {
-    #
-    # Get DESTDIR: first from ENV:DESTDIR, then the default
-    #
-    {
-        ini 1value ENV:DESTDIR | grep . && return
-        echo "$MKIT_DEFAULT_DESTDIR"
-    } \
-      | xargs readlink -m \
-      | grep -m 1 .
-}
-
 get_dst() {
     #
     # Find out target path for src file $2 of group $1
     local grp="$1"
     local root=$(ini 1value "roots:$grp")
     test -n "$root" || die "missing in config.ini: roots:$grp"
-    echo "$destdir/$root"
+    echo "$(ini 1value ENV:DESTDIR)$root"
 }
 
 install() {
     # Install product
     #
     local dst group mode src
-    local destdir=$(get_destdir)
-    check_env
     ini values "lists:group" \
       | while read group;
         do
     # Uninstall product
     #
     local dst group src
-    local destdir=$(get_destdir)
-    check_env
     ini values "lists:group" \
       | while read group;
         do

src/make.skel

 export MKIT_DIR=${MKIT_DIR:-$(dirname "$0")}
 export MKIT_LOCAL=${MKIT_LOCAL:-.mkit}
 export MKIT_DRY=${MKIT_DRY:-false}
-export MKIT_DEFAULT_DESTDIR=${MKIT_DEFAULT_DESTDIR:-/}
 export MKIT_DEBUG=${MKIT_DEBUG:-false}
 
 . "$MKIT_DIR/include/mkit.sh" || die "failed to init; check if MKIT_DIR is set properly: $MKIT_DIR"