[ruby/io-console] Define IO::ConsoleMode::VERSION from gemspec

https://github.com/ruby/io-console/commit/ebdbebf461

ext/io/console/console.c

@@ -1672,6 +1672,7 @@ InitVM_console(void)
     {
 	/* :stopdoc: */
         cConmode = rb_define_class_under(rb_cIO, "ConsoleMode", rb_cObject);
+        rb_define_const(cConmode, "VERSION", rb_str_new_cstr(STRINGIZE(IO_CONSOLE_VERSION)));
         rb_define_alloc_func(cConmode, conmode_alloc);
         rb_undef_method(cConmode, "initialize");
         rb_define_method(cConmode, "initialize_copy", conmode_init_copy, 1);

ext/io/console/extconf.rb

@@ -1,6 +1,11 @@
 # frozen_string_literal: false
 require 'mkmf'
 
+version = ["../../..", "."].find do |dir|
+  break File.read(File.join(__dir__, dir, "io-console.gemspec"))[/^_VERSION\s*=\s*"(.*?)"/, 1]
+rescue
+end
+
 have_func("rb_io_path")
 have_func("rb_io_descriptor")
 have_func("rb_io_get_write_io")
@@ -35,6 +40,7 @@ when true
   elsif have_func("rb_scheduler_timeout") # 3.0
     have_func("rb_io_wait")
   end
+  $defs << "-D""IO_CONSOLE_VERSION=#{version}"
   create_makefile("io/console") {|conf|
     conf << "\n""VK_HEADER = #{vk_header}\n"
   }