Fix external label in Bazel's C++ Tutorial.
Fix external label in Bazel's C++ Tutorial.

Fixes https://github.com/bazelbuild/bazel/issues/1786

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MOS_MIGRATED_REVID=134271340

zhexuany/bazel,katre/bazel,variac/bazel,katre/bazel,akira-baruah/bazel,ulfjack/bazel,Asana/bazel,dropbox/bazel,mbrukman/bazel,spxtr/bazel,akira-baruah/bazel,spxtr/bazel,mbrukman/bazel,snnn/bazel,perezd/bazel,cushon/bazel,twitter-forks/bazel,werkt/bazel,akira-baruah/bazel,kchodorow/bazel,LuminateWireless/bazel,meteorcloudy/bazel,dslomov/bazel,iamthearm/bazel,dslomov/bazel,ButterflyNetwork/bazel,meteorcloudy/bazel,mikelikespie/bazel,snnn/bazel,dslomov/bazel,cushon/bazel,twitter-forks/bazel,davidzchen/bazel,damienmg/bazel,twitter-forks/bazel,perezd/bazel,Asana/bazel,iamthearm/bazel,ButterflyNetwork/bazel,LuminateWireless/bazel,mrdomino/bazel,bazelbuild/bazel,dropbox/bazel,safarmer/bazel,mrdomino/bazel,kchodorow/bazel,variac/bazel,mikelikespie/bazel,snnn/bazel,kchodorow/bazel-1,twitter-forks/bazel,aehlig/bazel,twitter-forks/bazel,meteorcloudy/bazel,safarmer/bazel,davidzchen/bazel,safarmer/bazel,zhexuany/bazel,aehlig/bazel,damienmg/bazel,dslomov/bazel-windows,werkt/bazel,ulfjack/bazel,juhalindfors/bazel-patches,juhalindfors/bazel-patches,mikelikespie/bazel,mrdomino/bazel,damienmg/bazel,dslomov/bazel-windows,davidzchen/bazel,meteorcloudy/bazel,Asana/bazel,ButterflyNetwork/bazel,perezd/bazel,twitter-forks/bazel,mikelikespie/bazel,mikelikespie/bazel,bazelbuild/bazel,kchodorow/bazel-1,ulfjack/bazel,damienmg/bazel,meteorcloudy/bazel,cushon/bazel,aehlig/bazel,dropbox/bazel,spxtr/bazel,werkt/bazel,kchodorow/bazel-1,Asana/bazel,hermione521/bazel,mrdomino/bazel,perezd/bazel,juhalindfors/bazel-patches,juhalindfors/bazel-patches,aehlig/bazel,cushon/bazel,spxtr/bazel,katre/bazel,Asana/bazel,ulfjack/bazel,bazelbuild/bazel,spxtr/bazel,ButterflyNetwork/bazel,iamthearm/bazel,zhexuany/bazel,hermione521/bazel,aehlig/bazel,kchodorow/bazel,meteorcloudy/bazel,dslomov/bazel-windows,zhexuany/bazel,ulfjack/bazel,mrdomino/bazel,mbrukman/bazel,dslomov/bazel,meteorcloudy/bazel,dslomov/bazel,mbrukman/bazel,snnn/bazel,variac/bazel,damienmg/bazel,aehlig/bazel,safarmer/bazel,hermione521/bazel,kchodorow/bazel,katre/bazel,bazelbuild/bazel,spxtr/bazel,dropbox/bazel,davidzchen/bazel,variac/bazel,LuminateWireless/bazel,davidzchen/bazel,akira-baruah/bazel,safarmer/bazel,perezd/bazel,katre/bazel,variac/bazel,dslomov/bazel,ulfjack/bazel,kchodorow/bazel-1,variac/bazel,zhexuany/bazel,snnn/bazel,davidzchen/bazel,dslomov/bazel-windows,katre/bazel,cushon/bazel,ButterflyNetwork/bazel,perezd/bazel,twitter-forks/bazel,aehlig/bazel,Asana/bazel,juhalindfors/bazel-patches,werkt/bazel,mrdomino/bazel,variac/bazel,bazelbuild/bazel,hermione521/bazel,dslomov/bazel-windows,iamthearm/bazel,werkt/bazel,kchodorow/bazel-1,safarmer/bazel,akira-baruah/bazel,bazelbuild/bazel,LuminateWireless/bazel,kchodorow/bazel-1,perezd/bazel,dropbox/bazel,iamthearm/bazel,LuminateWireless/bazel,juhalindfors/bazel-patches,LuminateWireless/bazel,dropbox/bazel,dslomov/bazel-windows,hermione521/bazel,akira-baruah/bazel,ulfjack/bazel,dslomov/bazel,zhexuany/bazel,mbrukman/bazel,mbrukman/bazel,davidzchen/bazel,werkt/bazel,spxtr/bazel,ButterflyNetwork/bazel,mikelikespie/bazel,snnn/bazel,iamthearm/bazel,kchodorow/bazel,Asana/bazel,hermione521/bazel,damienmg/bazel,damienmg/bazel,cushon/bazel,juhalindfors/bazel-patches,kchodorow/bazel,snnn/bazel,kchodorow/bazel