Package bionic static libraries in the NDK.

Test: build/soong/scripts/build-ndk-prebuilts.sh
Bug: https://github.com/android-ndk/ndk/issues/272
Change-Id: Ibb21d799fdcf230ed45db0b809e20dd86d2d8e52
diff --git a/libc/Android.bp b/libc/Android.bp
index c81e8e5..a8c518d 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -1670,6 +1670,7 @@
 cc_library {
     defaults: ["libc_defaults"],
     name: "libc",
+    static_ndk_lib: true,
     product_variables: {
         platform_sdk_version: {
             asflags: ["-DPLATFORM_SDK_VERSION=%d"],
@@ -1782,6 +1783,7 @@
         "bionic/new.cpp",
     ],
     name: "libstdc++",
+    static_ndk_lib: true,
     system_shared_libs: ["libc"],
     static_libs: ["libasync_safe"],
 
diff --git a/libdl/Android.bp b/libdl/Android.bp
index 3889bdb..0603d06 100644
--- a/libdl/Android.bp
+++ b/libdl/Android.bp
@@ -25,6 +25,7 @@
 
 cc_library {
     name: "libdl",
+    static_ndk_lib: true,
 
     defaults: ["linux_bionic_supported"],
 
diff --git a/libm/Android.bp b/libm/Android.bp
index 6d6fafa..76a4699 100644
--- a/libm/Android.bp
+++ b/libm/Android.bp
@@ -6,6 +6,7 @@
 cc_library {
     name: "libm",
     defaults: ["linux_bionic_supported"],
+    static_ndk_lib: true,
 
     srcs: [
         "upstream-freebsd/lib/msun/bsdsrc/b_exp.c",