[clang-format] Add cmake target clang-format-style-options for updating ClangFormatStyleOptions.rst (llvm#111513)

* Create a new `clang-format-style-options` build target which
re-generates ClangFormatStyleOptions.rst from its source header files.

As discussed in
llvm#96804 (comment)

---------

Co-authored-by: Owen Pan <[email protected]>

Author: ichaer

clang/lib/Format/CMakeLists.txt

@@ -53,3 +53,13 @@ foreach (file IN LISTS files)
 endforeach ()
 
 add_custom_target(clang-format-check-format DEPENDS ${check_format_depends})
+
+set(style_options_depends ${CLANG_SOURCE_DIR}/docs/ClangFormatStyleOptions.rst)
+add_custom_command(OUTPUT ${style_options_depends}
+  COMMAND ${Python3_EXECUTABLE} dump_format_style.py
+  WORKING_DIRECTORY ${CLANG_SOURCE_DIR}/docs/tools
+  DEPENDS ${CLANG_SOURCE_DIR}/include/clang/Format/Format.h
+          ${CLANG_SOURCE_DIR}/include/clang/Tooling/Inclusions/IncludeStyle.h
+  )
+add_custom_target(clang-format-style-options DEPENDS ${style_options_depends})
+add_dependencies(clangFormat clang-format-style-options)