Update drone.yml

drone.yml

   environment:
     BUILDDEPS: build-essential libc6-dev libhidapi-dev libssl-dev   
     MAKEFLAGS: -j 4
+    MAKEDIRS: src          src/contrib
+    BINARIES: src/radangel src/contrib/websockify
   commands:
     - | 
       cat >> /etc/apt/apt.conf.d/01-proxy <<-EOF
     - apt-get update && apt-get --yes upgrade
     - apt-get --yes install $BUILDDEPS
     - export MAKEFLAGS
-    - make -C src
-    - make -C src/contrib
-    - ls -l  src/radangel src/contrib/websockify
-    - md5sum src/radangel src/contrib/websockify
+    - for DIR in $MAKEDIRS; do make -C $DIR ; done
+    - ls -l  $BINARIES && md5sum $BINARIES
   when:
     branch:
     - master