Gather lunch choices before printing prompt

Get the lunch choices before starting to print the lunch menu prompt
so that it doesn't sit at `Lunch menu... pick a combo:` with no
choices for a few seconds.

Fixes: 138719635
Test: lunch
Change-Id: I2bb373ec037bff0ab1d7e4f5ff8a8bd3b57f3263
diff --git a/envsetup.sh b/envsetup.sh
index 40f7705..92dad9a 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -575,6 +575,7 @@
 function print_lunch_menu()
 {
     local uname=$(uname)
+    local choices=$(TARGET_BUILD_APPS= get_build_var COMMON_LUNCH_CHOICES)
     echo
     echo "You're building on" $uname
     echo
@@ -582,7 +583,7 @@
 
     local i=1
     local choice
-    for choice in $(TARGET_BUILD_APPS= get_build_var COMMON_LUNCH_CHOICES)
+    for choice in $choices
     do
         echo "     $i. $choice"
         i=$(($i+1))