Log message:
cxxopts: update to 3.1.1

3.1.1

Fix version number in header.

3.1.0

- Support for multiple long names for the same option (= multiple long aliases)
- Add a program() function to retrieve the program name.
- Added a .clang-format file.
- Added iterator and printing for a ParseResult.
- Cleanup exception code, add cxxopts::exceptions namespace.
- Fix arguments() having no key for options that only have a short name.

Log message:
cxxopts: set DEPMETHOD to build since it only installs a header

Log message:
Add cxxopts-3.0.0

This is a lightweight C++ option parser library, supporting the
standard GNU style syntax for options.

Options can be given as:

  --long
  --long=argument
  --long argument
  -a
  -ab
  -abc argument

where c takes an argument, but a and b do not.

Additionally, anything after -- will be parsed as a positional
argument.