[libcxx-commits] [libcxx] [libcxx] Update testing documentation about CI container images. (PR #149192)

[Aiden Grossman via libcxx-commits]

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@@ -261,6 +264,67 @@ GCC, and CMake.
 .. note:: This image is pulled from Docker hub and not rebuild when changing
    the Dockerfile.
 
+Updating the CI testing container images
+----------------------------------------
+
+The libcxx linux premerge testing can run on one of three sets of
+runner groups. The three runner group names are
+"llvm-premerge-libcxx-runners", "llvm-premerge-libcxx-release-runners"
+or "llvm-premerge-libcxx-next-runners".  Which runner set to use is
+controlled by the contents of https://github.com/llvm/llvm-project/blob/main/.github/workflows/libcxx-build-and-test.yaml . By default, it uses
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boomanaiden154 wrote:

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https://github.com/llvm/llvm-project/pull/149192