[libcxx] [llvm] [libcxx] Simplify container images (PR #225214)

[Nikolas Klauser via llvm-commits]

================
@@ -6,33 +6,138 @@
 #
 # ===----------------------------------------------------------------------===##
 #
-# This file defines the image we use for Linux testing using Github Actions.
+# This file defines the base image we use for Linux testing using Github Actions.
 # From the root of the monorepo, this image can be built with:
 #
-#   $ docker build --file libcxx/utils/ci/docker/linux-builder.dockerfile \
-#                  --build-arg BASE_IMAGE_VERSION=<sha>                   \
-#                  --build-arg GITHUB_RUNNER_VERSION=<version> .
+#   $ docker build --file libcxx/utils/ci/docker/linux-builder-base.dockerfile \
----------------
philnik777 wrote:

```suggestion
#   $ docker build --file libcxx/utils/ci/docker/linux-builder.dockerfile \
```

https://github.com/llvm/llvm-project/pull/225214