Added SSH awareness.

This should be used with

```
ifndef IS_SSH
```

I will try and move IS_MAC and IS_LINUX to work with this as well. Issue I'm
having is or statements.

lib/shared.mk

@@ -27,6 +27,8 @@ endif
 IS_MAC?=false
 IS_LINUX?=false
 
+IS_SSH=${SSH_TTY}
+
 # TURN THIS OFF FOR DEBUGGING
 MAKEFLAGS += --silent