minadbd: track adb C++ version change.

adb is going to start using shiny new C++17 features like
std::optional in headers that minadbd includes.

Test: mma
Change-Id: I7eb100c48abbf2364d6ff5f30aa223480e2466a6
diff --git a/minadbd/Android.bp b/minadbd/Android.bp
index 370232b..7e33261 100644
--- a/minadbd/Android.bp
+++ b/minadbd/Android.bp
@@ -15,6 +15,7 @@
 cc_defaults {
     name: "minadbd_defaults",
 
+    cpp_std: "gnu++17",
     cflags: [
         "-DADB_HOST=0",
         "-Wall",