Suppress certain warinings in Android build

Test: mm
Change-Id: Iaea6f2e23e33468435699a93089b4541ff62ffb5
diff --git a/Android.bp b/Android.bp
index 2f7a574..3fb7b61 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1742,6 +1742,7 @@
         "-Wno-unused-parameter",
         "-Wno-missing-field-initializers",
         "-Wno-pointer-arith",
+        "-Wno-implicit-function-declaration",
     ],
     stl: "libc++_static",
 }