Add modules for NDK headers and libraries.

Test: make checkbuild
Bug: http://b/27533932
Change-Id: I285e483ba9fb80cc3baf0d025c85344e5b79a08b
diff --git a/libm/Android.bp b/libm/Android.bp
index 23b9d5e..64d281f 100644
--- a/libm/Android.bp
+++ b/libm/Android.bp
@@ -531,3 +531,9 @@
     },
     stl: "none",
 }
+
+ndk_library {
+    name: "libm.ndk",
+    symbol_file: "libm.map.txt",
+    first_version: "9",
+}