Add support for multiple variable overrides

Now we can do:

$ b config.cxx.coptions=-O3 config.cxx.coptions=-O0

Or even:

$ b config.cxx.coptions=-O3 config.cxx.coptions+=-g

1 files changed, 1 insertions, 1 deletions

diff --git a/build2/parser.cxx b/build2/parser.cxx
index 3acff37..997a1ac 100644
--- a/build2/parser.cxx
+++ b/build2/parser.cxx
@@ -5108,7 +5108,7 @@ namespace build2
       if (!r.first.defined ())
         r = t->find_original (var);
 
-      return var.override == nullptr
+      return var.overrides == nullptr
         ? r.first
         : t->base_scope ().find_override (var, move (r), true).first;
     }