[clang-format] [PR45126] Help text is missing all available formats

Summary:
https://bugs.llvm.org/show_bug.cgi?id=45126

GNU and Microsoft styles are built in supported styles but are not displayed in the help text

Reviewed By: sammccall

Subscribers: cfe-commits

Tags: #clang, #clang-format

Differential Revision: https://reviews.llvm.org/D79372