MakeMakefile#find_header

# File tmp/rubies/ruby-3.3.0/lib/mkmf.rb, line 1199
def find_header(header, *paths)
  message = checking_message(header, paths)
  header = cpp_include(header)
  checking_for message do
    if try_header(header)
      true
    else
      found = false
      paths.each do |dir|
        opt = "-I#{dir}".quote
        if try_header(header, opt)
          $INCFLAGS << " " << opt
          found = true
          break
        end
      end
      found
    end
  end
end