caddy1: fix build (#97988)

main.go gets overwritten in order to build caddy with telemetry
disabled, but the global variable `run` got neglected, and this in turn
broke the test in caddy/main_test.go.

This commit fixes that, and build can now complete.

Changed files
+2 -1
pkgs
servers
caddy
+2 -1
pkgs/servers/caddy/v1.nix
···
cat << EOF > caddy/main.go
package main
import "github.com/caddyserver/caddy/caddy/caddymain"
+
var run = caddymain.Run // replaced for tests
func main() {
caddymain.EnableTelemetry = false
-
caddymain.Run()
+
run()
}
EOF
'';