ruby.c: dladdr_path is not used on cygwin

* ruby.c (dladdr_path): dladdr is provided on recent cygwin, but
  GetModuleFileNameW is used instead of it.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59007 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ruby.c

@@ -439,7 +439,7 @@ ruby_init_loadpath(void)
     ruby_init_loadpath_safe(0);
 }
 
-#if defined(LOAD_RELATIVE) && defined(HAVE_DLADDR)
+#if defined(LOAD_RELATIVE) && defined(HAVE_DLADDR) && !defined(__CYGWIN__)
 static VALUE
 dladdr_path(const void* addr)
 {