[libc++] Only upload generated abilists.

[Mordante]

Summary

Only upload the abilist that's generated on that platform.

Note, there are no reviewers yet since first want to test it on
buildkite.

[Mordante]

Discussed this in private with @ldionne and we don't want to move into this direction. The intention is that the build jobs are generic.

libcxx/utils/ci/buildkite-pipeline.yml

retry:
           limit: 2
     soft_fail:
         - exit_status: 1
 
   - label: "C++03"
     command: "libcxx/utils/ci/run-buildbot generic-cxx03"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*linux*.abilist"
     agents:
       queue: "libcxx-builders"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "C++11"
     command: "libcxx/utils/ci/run-buildbot generic-cxx11"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*linux*.abilist"
     agents:
       queue: "libcxx-builders"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "C++14"
     command: "libcxx/utils/ci/run-buildbot generic-cxx14"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*linux*.abilist"
     agents:
       queue: "libcxx-builders"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "C++17"
     command: "libcxx/utils/ci/run-buildbot generic-cxx17"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*linux*.abilist"
     agents:
       queue: "libcxx-builders"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "C++20"
     command: "libcxx/utils/ci/run-buildbot generic-cxx20"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*linux*.abilist"
     agents:
       queue: "libcxx-builders"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "C++2b"
     command: "libcxx/utils/ci/run-buildbot generic-cxx2b"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*linux*.abilist"
     agents:
       queue: "libcxx-builders"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "-fno-exceptions"
retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "MacOS C++20"
     command: "libcxx/utils/ci/run-buildbot generic-cxx20"
     artifact_paths:
       - "**/test-results.xml"
-      - "**/*.abilist"
+      - "**/*apple*.abilist"
     agents:
       queue: "libcxx-builders-macos"
     retry:
       automatic:
         - exit_status: -1  # Agent was lost
           limit: 2
 
   - label: "Benchmarks"