fix(ci): adjust custom build to fix needs on master.

.gitlab-ci.yml

@@ -77,6 +77,10 @@ microsoftstore_qt515:
     key: "CCACHE-DB-$CI_PROJECT_ID"
     paths: [ "${CCACHE_DIR}" ]
     when: always
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+    - allow_failure: true
+      when: manual
   before_script:
     - du -hs "${CCACHE_DIR}" || mkdir -p "${CCACHE_DIR}"
     - add-apt-repository --remove ppa:mutlaqja/indinightly
@@ -91,9 +95,6 @@ microsoftstore_qt515:
 build:
   stage: build
   extends: .custom_build
-  only:
-    - master
-    - merge_requests
   script:
     - cd kstars-build
     - cmake -GNinja -DCMAKE_BUILD_TYPE=Release -DCCACHE_SUPPORT=ON -DBUILD_TESTING=OFF -DBUILD_DOC=OFF ..
@@ -109,8 +110,6 @@ build-and-test-stable:
   needs:
     - build
   timeout: 3 hours
-  only:
-    - merge_requests
   variables:
     BUILD_TESTING: "ON"
   script: