CI: only send notification on failure or change of status

.drone.yml

@@ -7,14 +7,14 @@ platform:
   arch: arm64
 
 steps:
-#- name: build
-#  image: docker.zvon.tech/cppbuilder:v0.06
-#  commands:
-#  - cd mario
-#  - mkdir build
-#  - cd build
-#  - cmake ..
-#  - make
+- name: build
+  image: docker.zvon.tech/cppbuilder:v0.06
+  commands:
+  - cd mario
+  - mkdir build
+  - cd build
+  - cmake ..
+  - make
 - name: formatting-check
   image: docker.zvon.tech/cppbuilder:v0.06
   commands:
@@ -34,3 +34,5 @@ steps:
       from_secret: email_password
     port: 465
     from: Drone <drone@zvon.tech>
+  when:
+    status: [ changed, failure ]