Merge #18106: test: Disable s390 build on travis

b0a01299ed test: Disable s390 build on travis (Wladimir J. van der Laan)

Pull request description:

  Travis is consistently failing on s390 due to out of disk space issues,
  which causes false positives. Disable the s390 build for now until
  this is fixed some other way.

ACKs for top commit:
  MarcoFalke:
    ACK b0a01299ed 🍠
  jonasschnelli:
    ACK b0a01299ed

Tree-SHA512: ae8a78fa03bc620d802e4992d46929a0a4b801b50a6066d8f093f93fc5ebbc010d221c04787cbfc75436a2c40f9292257bf85fbb251593e21afff11756b6d8d4

.travis.yml

@@ -88,12 +88,14 @@ jobs:
         FILE_ENV="./ci/test/00_setup_env_arm.sh"
         QEMU_USER_CMD=""  # Can run the tests natively without qemu
 
-    - stage: test
-      name: 'S390x  [GOAL: install]  [buster]  [unit tests, functional tests]'
-      arch: s390x
-      env: >-
-        FILE_ENV="./ci/test/00_setup_env_s390x.sh"
-        QEMU_USER_CMD=""  # Can run the tests natively without qemu
+# s390 build was disabled temporarily because of disk space issues on the Travis VM
+#
+#    - stage: test
+#      name: 'S390x  [GOAL: install]  [buster]  [unit tests, functional tests]'
+#      arch: s390x
+#      env: >-
+#        FILE_ENV="./ci/test/00_setup_env_s390x.sh"
+#        QEMU_USER_CMD=""  # Can run the tests natively without qemu
 
     - stage: test
       name: 'Win64  [GOAL: deploy]  [unit tests, no gui, no functional tests]'