[libc++] Move macOS testing out of the 2nd CI stage

It's too slow, which delays the posting of CI results to Phabricator
when another step in the same stage fails.

diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
index 6dfb1bf..ebcc346 100644 (file)
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -48,8 +48,8 @@ steps:
 
   #
   # General testing with the default configuration, under all the supported
-  # Standard modes, with Clang and GCC and on Apple. This catches most issues
-  # upfront.
+  # Standard modes, with Clang and GCC. This catches most issues upfront.
+  # The goal of this step is to catch most issues while being very fast.
   #
   - wait
 
@@ -125,18 +125,6 @@ steps:
         - 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"
-    agents:
-      queue: "libcxx-builders-macos"
-    retry:
-      automatic:
-        - exit_status: -1  # Agent was lost
-          limit: 2
-
   - label: "GCC/C++20"
     command: "libcxx/utils/ci/run-buildbot generic-gcc"
     artifact_paths:
@@ -342,6 +330,18 @@ steps:
         - 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"
+    agents:
+      queue: "libcxx-builders-macos"
+    retry:
+      automatic:
+        - exit_status: -1  # Agent was lost
+          limit: 2
+
   # Build with the configuration we use to generate libc++.dylib on Apple platforms
   - label: "Apple system"
     command: "libcxx/utils/ci/run-buildbot x86_64-apple-system"