MakeMakefile#create_tmpsrc

# File tmp/rubies/ruby-4.0.0/lib/mkmf.rb, line 495
def create_tmpsrc(src)
  src = "#{COMMON_HEADERS}\n#{src}"
  src = yield(src) if block_given?
  src.gsub!(/[ \t]+$/, '')
  src.gsub!(/\A\n+|^\n+$/, '')
  src.sub!(/[^\n]\z/, "\\&\n")
  count = 0
  begin
    File.open(conftest_source, "wb") do |cfile|
      cfile.print src
    end
  rescue Errno::EACCES
    if (count += 1) < 5
      sleep 0.2
      retry
    end
  end
  src
end