Remove improper ifdef
diff --git a/config.m4 b/config.m4
index 86e6aa8..dbab825 100644
--- a/config.m4
+++ b/config.m4
@@ -257,6 +257,7 @@
     src/core/ext/resolver/dns/c_ares/dns_resolver_ares.c \
     src/core/ext/resolver/dns/c_ares/grpc_ares_ev_driver_posix.c \
     src/core/ext/resolver/dns/c_ares/grpc_ares_wrapper.c \
+    src/core/ext/resolver/dns/c_ares/grpc_ares_wrapper_fallback.c \
     src/core/ext/resolver/dns/native/dns_resolver.c \
     src/core/ext/resolver/sockaddr/sockaddr_resolver.c \
     src/core/ext/load_reporting/load_reporting.c \