Replace soong variables with cc_defaults.

Bug: 64318482
Test: links
Change-Id: Id03af485a4282db5b9a13a79fce00a2d66b59ffc
diff --git a/base/Android.bp b/base/Android.bp
index 5a38ed8..5d79e81 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -19,7 +19,7 @@
         enabled: true,
         support_system_process: true,
     },
-    cflags: libhidl_flags,
+    defaults: ["libhidl-defaults"],
     shared_libs: [
         "libbase",
         "libcutils",