dabuild: create mount directories with correct permissions

docker creates mount points as root when source does not exists instead
create them first with UID 1000 which should be the UID of the builder
user inside the container.

dabuild.in

@@ -58,10 +58,13 @@ else
   esac
 fi
 
-## check $DABUILD_PACKAGES is a writable directory
 ABUILD_PACKAGES=${DABUILD_PACKAGES:-${PWD%/aports/*}/packages/${ABUILD_VERSION}}
 
-mkdir -p $ABUILD_PACKAGES
+# docker will create mount points as root if not available so create them first
+# use uid 1000 as this is the uid of the builder user in the container
+install -d -o 1000 -g 1000 "$ABUILD_PACKAGES" "$HOME"/.abuild
+
+## check $DABUILD_PACKAGES is a writable directory
 if [ ! \( -d "$ABUILD_PACKAGES" -a -w "$ABUILD_PACKAGES" \) ]; then
   die "Error: invalid or unwritable packages directory specified!" \
       "ABUILD_PACKAGES = '$ABUILD_PACKAGES'" \