cmd/dist: remove external linking check for macOS 10.6
cmd/dist: remove external linking check for macOS 10.6

This was missed in CL 115236.

Updates #23122

Change-Id: I5a64bd02d356c21c0e5d02dafafb3721f8dd8e06
Reviewed-on: https://go-review.googlesource.com/115276
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

cloudflare/go,cloudflare/go,akutz/go,cloudflare/go,nawawi/go,nawawi/go,CAFxX/go,josharian/go,josharian/go,golang/go,CAFxX/go,akutz/go,nawawi/go,golang/go,josharian/go,akutz/go,CAFxX/go,nawawi/go,akutz/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,josharian/go,golang/go,nawawi/go,akutz/go,akutz/go,nawawi/go,cloudflare/go,golang/go,josharian/go,CAFxX/go,nawawi/go,josharian/go,akutz/go,CAFxX/go,nawawi/go,cloudflare/go,josharian/go,CAFxX/go,golang/go,golang/go,akutz/go,cloudflare/go,josharian/go,golang/go,CAFxX/go