Upstream ninja is sticking with C++14.

Bug: http://b/111067277
Test: builds
Change-Id: If12232137f129c7cec708e71ab974925b02abe1e
diff --git a/Android.bp b/Android.bp
index a243f51..a78fab5 100644
--- a/Android.bp
+++ b/Android.bp
@@ -25,6 +25,7 @@
         "-DNINJA_PYTHON=\"python\"",
         "-DNINJA_HAVE_BROWSE",
     ],
+    cpp_std: "c++14",
     target: {
         linux_glibc: {
             cflags: ["-DUSE_PPOLL"],