[dev.cc] runtime/cgo: convert from C to Go

The conversion was done with an automated tool and then
modified only as necessary to make it compile and run.

[This CL is part of the removal of C code from package runtime.
See golang.org/s/dev.cc for an overview.]

LGTM=r
R=r
CC=austin, dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/168500043
diff --git a/src/runtime/cgo/dragonfly.go b/src/runtime/cgo/dragonfly.go
new file mode 100644
index 0000000..96eb866
--- /dev/null
+++ b/src/runtime/cgo/dragonfly.go
@@ -0,0 +1,19 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build dragonfly
+
+package cgo
+
+import _ "unsafe"
+
+// Supply environ and __progname, because we don't
+// link against the standard DragonFly crt0.o and the
+// libc dynamic library needs them.
+
+//go:linkname _environ environ
+//go:linkname _progname __progname
+
+var _environ uintptr
+var _progname uintptr