wip: custom environment variable passing

You should be able to tell your sci deployment which env vars should be
passed to the pipelines with -e ENV1 -e ENV2 and so on

include/optional.h

@@ -17,6 +17,7 @@
  */
 #ifndef SCI_OPTIONAL_H
 #define SCI_OPTIONAL_H
+#include "strlist.h"
 #include <stdbool.h>
 
 #define optional_type(type) struct { bool has_value; type value; }
@@ -24,5 +25,6 @@ typedef optional_type(int) optional_int;
 typedef optional_type(float) optional_float;
 typedef optional_type(char*) optional_str;
 typedef optional_type(const char*) optional_cstr;
+typedef optional_type(strlist_node*) optional_strlist;
 
 #endif