make.bash: more robustly detect gold 2.20
make.bash: more robustly detect gold 2.20

On recent Debian systems the gold 2.20 check triggers though
Debian doesn't have version 2.20 but rather has:

        GNU gold (GNU Binutils for Debian 2.21.52.20110606) 1.11
                                                ^^^^

R=rsc, iant
CC=golang-dev
http://codereview.appspot.com/5252055

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

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