Fixes Uno on MacOS (#190)

diff --git a/bin/impl/util.sh b/bin/impl/util.sh
index dcdc40e..14c75e8 100755
--- a/bin/impl/util.sh
+++ b/bin/impl/util.sh
@@ -61,7 +61,7 @@
 }
 
 function save_console_fd {
-  if [[ -z "$UNO_CONSOLE_FD" ]]; then
+  if [[ -z "$UNO_CONSOLE_FD" && "$OSTYPE" != "darwin"* ]]; then
     # Allocate an unused file descriptor and make it dup stdout
     # https://stackoverflow.com/a/41620630/7298689
     exec {UNO_CONSOLE_FD}>&1