ci: reintroduce prevention from perforce being quarantined in macOS

5ed9fc3fc8 (ci: prevent `perforce` from being quarantined, 2020-02-27)
introduces this prevention for brew, but brew has been removed in a
previous commit, so reintroduce an equivalent option to avoid a possible
regression.

This doesn't affect github actions (as configure now) and is therefore
done silently to avoid any possible scary irrelevant messages.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ci/install-dependencies.sh

@@ -41,7 +41,8 @@ macos-latest)
 	(
 		cd $HOME/bin
 		wget -q "https://cdist2.perforce.com/perforce/r21.2/bin.macosx1015x86_64/helix-core-server.tgz" &&
-		tar -xf helix-core-server.tgz
+		tar -xf helix-core-server.tgz &&
+		sudo xattr -d com.apple.quarantine p4 p4d 2>/dev/null || true
 	)
 	PATH="$PATH:${HOME}/bin"
 	export PATH