[C++] Fix value.mk
diff --git a/parser.cc b/parser.cc
index d185b51..ccb88de 100644
--- a/parser.cc
+++ b/parser.cc
@@ -197,6 +197,7 @@
     ast->set_loc(loc_);
     ast->lhs = ParseExpr(lhs);
     ast->rhs = ParseExpr(rhs);
+    ast->orig_rhs = rhs;
     ast->op = op;
     ast->directive = AssignDirective::NONE;
     out_asts_->push_back(ast);
@@ -241,6 +242,7 @@
     if (define_start_)
       rhs = TrimRightSpace(buf_.substr(define_start_, l_ - define_start_));
     ast->rhs = ParseExpr(rhs, ParseExprOpt::DEFINE);
+    ast->orig_rhs = rhs;
     ast->op = AssignOp::EQ;
     ast->directive = AssignDirective::NONE;
     out_asts_->push_back(ast);