chore: import upstream snapshot with attribution

third_party/xla/docs/developer_environment.md

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+# Setting Up Developer Environment
+
+## Setting up LSP with clangd
+
+### Background
+
+Editors such as Emacs, Vim, or VS Code support features like code navigation,
+code completion, inline compiler error messages, and others, through
+[LSP](https://en.wikipedia.org/wiki/Language_Server_Protocol), the Language
+Server Protocol. A common language server with LSP support is
+[clangd](https://clangd.llvm.org), which relies on the presence of
+`compile_commands.json`, a JSON file with a record of the compile commands for
+each file in a project.
+
+### How do I generate `compile_commands.json` for XLA source code?
+
+Use the
+[build_tools/lint/generate_compile_commands.py](https://github.com/openxla/xla/blob/main/build_tools/lint/generate_compile_commands.py)
+script. The following invocation from XLA repo root generates a
+`compile_commands.json` file in place: `bazel aquery "mnemonic(CppCompile,
+//xla/...)" --output=jsonproto | python3
+build_tools/lint/generate_compile_commands.py`
+
+## Build Cleaner
+
+XLA CI inside Google runs additional checks to verify that all targets correctly
+list all dependencies in the BUILD files, which are not enabled by default in
+OSS Bazel CI. Running following commands before sending PR to XLA team will
+massively speedup the time it takes to merge the PR as otherwise you will need
+some Googler to make this fixes for you internally, or a few more rounds of PR
+reviews to fix them based on the Googlers feedback.
+
+### Layering Check
+
+Building with `--features=layering_check` makes sure that you don't accidentally
+include a header via transitive dependency without listing it in your target
+dependencies
+
+### Remove unused dependencies from BUILD files
+
+Install
+[Buildozer](https://github.com/bazelbuild/buildtools/blob/main/buildozer/README.md)
+tool:
+
+```
+sudo curl -fsSL -o /usr/bin/buildozer https://github.com/bazelbuild/buildtools/releases/download/6.0.0/buildozer-linux-amd64
+sudo chmod 755 /usr/bin/buildozer
+```
+
+Install [Bant](https://github.com/hzeller/bant) tool:
+
+```
+# To some writable directory that does not require root access
+bazel build -c opt //bant && install -D --strip bazel-bin/bant/bant ~/bin/bant
+
+# For a system directory that requires root-access
+sudo install -D --strip bazel-bin/bant/bant /usr/local/bin/bant
+```
+
+Use `bant` to generate buildozer commands to remove unused deps:
+
+```
+bant dwyu //xla/core/collectives:symmetric_memory
+```
+
+if you feel lucky, you can execute them directly:
+
+```
+. <(bant dwyu //xla/core/collectives:symmetric_memory)
+```