1.2.1

CHANGES:

• Enrich the dune Emacs mode with syntax highlighting and indentation. New
  file dune-flymake to provide a hook dune-flymake-dune-mode-hook to enable
  linting of dune files. (#1265, @Chris00)

• Pass link_flags to cc when compiling with Configurator.V1.c_test (#1274,
  @rgrinberg)

• Fix digest calculation of aliases. It should take into account extra bindings
  passed to the alias (#1277, fix #1276, @rgrinberg)

• Fix a bug causing dune to fail eagerly when an optional library
  isn't available (#1281, @diml)

• ocamlmklib should use response files only if ocaml >= 4.08 (@1268, @bryphe)