nixos/prometheus/alertmanager: double hyphenate long opts (#34914)

Alertmanager 0.13.0 doesn't support single dash long options, so '-config.file'
for example is parsed as '-c', which leads to the service not starting.

Changed files
+5 -5
nixos
modules
services
monitoring
prometheus
+5 -5
nixos/modules/services/monitoring/prometheus/alertmanager.nix
···
after = [ "network.target" ];
script = ''
${pkgs.prometheus-alertmanager.bin}/bin/alertmanager \
-
-config.file ${alertmanagerYml} \
-
-web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
-
-log.level ${cfg.logLevel} \
-
${optionalString (cfg.webExternalUrl != null) ''-web.external-url ${cfg.webExternalUrl} \''}
-
${optionalString (cfg.logFormat != null) "-log.format ${cfg.logFormat}"}
+
--config.file ${alertmanagerYml} \
+
--web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
+
--log.level ${cfg.logLevel} \
+
${optionalString (cfg.webExternalUrl != null) ''--web.external-url ${cfg.webExternalUrl} \''}
+
${optionalString (cfg.logFormat != null) "--log.format ${cfg.logFormat}"}
'';
serviceConfig = {