macOS 10.12 brew install openssl issue

I managed to resolve it by editing formula (brew edit openssl)
and adding

-I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include

to args array in configure_args.

As below:

  def configure_args
    args = %W[
      --prefix=#{prefix}
      --openssldir=#{openssldir}
      no-ssl3
      no-ssl3-method
      no-zlib
      ##### add the line here ####
      -I/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include
    ]
    on_linux do
      args += (ENV.cflags || "").split
      args += (ENV.cppflags || "").split
      args += (ENV.ldflags || "").split
      args << "enable-md2"
    end
    args
  end