[libc++] Temporarily disable FreeBSD runners

They have been out for over 10 days, which only causes confusion
when looking at CI results.

Author: ldionne

libcxx/utils/ci/buildkite-pipeline.yml

@@ -115,17 +115,19 @@ steps:
       os: aix
     <<: *common
 
-- group: ':freebsd: FreeBSD'
-  steps:
-  - label: FreeBSD 13 amd64
-    command: libcxx/utils/ci/run-buildbot generic-cxx26
-    env:
-      CC: clang17
-      CXX: clang++17
-    agents:
-      queue: libcxx-builders
-      os: freebsd
-    <<: *common
+# TODO: Re-enable this when the FreeBSD runners are back online
+#       https://github.com/llvm/llvm-project/issues/117780
+# - group: ':freebsd: FreeBSD'
+#   steps:
+#   - label: FreeBSD 13 amd64
+#     command: libcxx/utils/ci/run-buildbot generic-cxx26
+#     env:
+#       CC: clang17
+#       CXX: clang++17
+#     agents:
+#       queue: libcxx-builders
+#       os: freebsd
+#     <<: *common
 
 - group: ':android: Android'
   steps: