[CI] Improve docker ci for other PRs (#4051)

* Adding self to trigger a build in the future

* Push only on PCL/master

.ci/azure-pipelines/env.yml

@@ -9,11 +9,13 @@ trigger:
   paths:
     include:
     - .dev/docker/env/Dockerfile
+    - .ci/azure-pipelines/env.yml
 
 pr:
   paths:
     include:
     - .dev/docker/env/Dockerfile
+    - .ci/azure-pipelines/env.yml
 
 schedules:
 - cron: "0 0 * * 0"
@@ -53,6 +55,7 @@ jobs:
         CUDA_VERSION: 11
         UBUNTU_DISTRO: 20.04
         VTK_VERSION: 7
+        # nvidia-cuda docker image has not been released for 20.04 yet
         USE_CUDA: ""
         tag: 20.04
   steps:
@@ -87,4 +90,5 @@ jobs:
       containerRegistry: $(dockerHub)
       repository: $(dockerHubID)/env
       tags: "$(tag)"
-      condition: eq(variables['Build.SourceBranch'], 'refs/heads/master')
+      condition: and(eq(variables['Build.Repository.Name'], 'PointCloudLibrary/pcl'),
+                     eq(variables['Build.SourceBranch'], 'refs/heads/master'))