[clang-format] Add test to ensure formatting options docs are updated

This patch adds a lit test to clang format to ensure that the
ClangFormatStyleOptions doc page has been updated appropriately. The
test just runs the automatic update script and diffs the outputs to
ensure they are the same.

Author: boomanaiden154

clang/docs/tools/dump_format_style.py

@@ -487,5 +487,6 @@ class State:
 
 contents = substitute(contents, "FORMAT_STYLE_OPTIONS", options_text)
 
-with open(DOC_FILE, "wb") as output:
+output_file_path = sys.argv[1] if len(sys.argv) == 2 else DOC_FILE
+with open(output_file_path, "wb") as output:
     output.write(contents.encode())

clang/test/Format/docs_updated.test

@@ -0,0 +1,2 @@
+// RUN: %python %S/../../docs/tools/dump_format_style.py %t
+// RUN: diff %t %S/../../docs/ClangFormatStyleOptions.rst

clang/test/Format/lit.local.cfg

@@ -17,4 +17,5 @@ config.suffixes = [
     ".textpb",
     ".asciipb",
     ".td",
+    ".test"
 ]