--- a/build	Mon Jun 15 17:29:46 2015 +0200
+++ b/build	Mon Jun 15 17:30:56 2015 +0200
@@ -1,14 +1,18 @@
 #!/bin/bash
 
+set -e
 trap '[[ $SORRY ]] && echo "FAILED: $SORRY" >&2' EXIT
+
+# update the Dockerfiles for the platforms
 make -C platforms
-set -e
+
 test -d exim || {
     echo "exim src directory missing" >&2
     echo "try: git clone https://github.com/Exim/exim.git" >&2
     exit 1
 }
-for dockerfile in ${*:-platforms/*/Dockerfile}
+
+for dockerfile in $(find "${@-platforms}" -name Dockerfile)
 do
     context=${dockerfile%/*}
     system=${context#*/}