Move export statement to correct position

.drone.yml

@@ -31,7 +31,6 @@ pipeline:
       group: build
       pull: true
       commands:
-        - export PATH=/Users/macosvm/flutter/bin:$PATH
         - flutter packages get
         - make build-all
         - mkdir apks
@@ -46,6 +45,7 @@ pipeline:
       port: 2222
       secrets: [ ssh_username, ssh_key ]
       script:
+        - export PATH=/Users/macosvm/flutter/bin:$PATH
         - cd /tmp/drone_build_${DRONE_BUILD_NUMBER}
         - flutter packages get
         - make build-ios-all