[clang] [clang-format][CMake] Generate formatting options docs during build (PR #113739)

[Owen Pan via cfe-commits]

================
@@ -143,8 +143,17 @@ if (LLVM_ENABLE_SPHINX)
     gen_rst_file_from_td(DiagnosticsReference.rst -gen-diag-docs ../include/clang/Basic/Diagnostic.td "${docs_targets}")
     gen_rst_file_from_td(ClangCommandLineReference.rst -gen-opt-docs ../include/clang/Driver/ClangOptionDocs.td "${docs_targets}")
 
+    add_custom_target(clang-format-style-options
+      COMMAND "${Python3_EXECUTABLE}" "${CLANG_SOURCE_DIR}/docs/tools/dump_format_style.py"
----------------
owenca wrote:

```suggestion
    set (dump_format_style ${CLANG_SOURCE_DIR}/docs/tools/dump_format_style.py)
    add_custom_target(clang-format-style-options
      COMMAND ${Python3_EXECUTABLE} ${dump_format_style}
```
See below.

https://github.com/llvm/llvm-project/pull/113739