envsetup.sh: Update text in lunch menu for clarity

Updates the lunch menu text to make it clearer that the choices in lunch
menu are not fully comprehensive. As the list comes from common lunch
choices the text now refers to 'common combinations' and informs that
you can 'specify your own'. This should help developers who are unsure
why they cannot find their desired lunch target in the list.

Change-Id: Ib9d55ee46b7037c30a8f4b43fdd552ea66e887e8
Test: source build/envsetup.sh && lunch

envsetup.sh

@@ -625,7 +625,7 @@ function print_lunch_menu()
         return
     fi
 
-    echo "Lunch menu... pick a combo:"
+    echo "Lunch menu .. Here are the common combinations:"
 
     local i=1
     local choice
@@ -647,12 +647,16 @@ function lunch()
         return 1
     fi
 
+    local used_lunch_menu=0
+
     if [ "$1" ]; then
         answer=$1
     else
         print_lunch_menu
-        echo -n "Which would you like? [aosp_arm-eng] "
+        echo "Which would you like? [aosp_arm-eng]"
+        echo -n "Pick from common choices above (e.g. 13) or specify your own (e.g. aosp_barbet-eng): "
         read answer
+        used_lunch_menu=1
     fi
 
     local selection=
@@ -717,6 +721,11 @@ function lunch()
     fi
     export TARGET_BUILD_TYPE=release
 
+    if [ $used_lunch_menu -eq 1 ]; then
+      echo
+      echo "Hint: next time you can simply run 'lunch $selection'"
+    fi
+
     [[ -n "${ANDROID_QUIET_BUILD:-}" ]] || echo
 
     set_stuff_for_environment