Add native libraries to gn apks

build/config/android/config.gni

Index: build/config/android/config.gni
diff --git a/build/config/android/config.gni b/build/config/android/config.gni
index f509677441556829dc79c1ec297ec4c1280c11a4..29d739a438791267ddcbd770c2e54dfe0dac6135 100644
--- a/build/config/android/config.gni
+++ b/build/config/android/config.gni
@@ -87,14 +87,20 @@ if (is_android) {
   # only need to define the current one, rather than one for every platform
   # like the toolchain roots.
   if (cpu_arch == "x86") {
+    android_prebuilt_arch = "android-x86"
+    _binary_prefix = "i686-linux-android"
     android_toolchain_root = "$x86_android_toolchain_root"
     android_libgcc_file =
       "$android_toolchain_root/lib/gcc/i686-linux-android/${_android_toolchain_version}/libgcc.a"
   } else if (cpu_arch == "arm") {
+    android_prebuilt_arch = "android-arm"
+    _binary_prefix = "arm-linux-androideabi"
     android_toolchain_root = "$arm_android_toolchain_root"
     android_libgcc_file =
       "$android_toolchain_root/lib/gcc/arm-linux-androideabi/${_android_toolchain_version}/libgcc.a"
   } else if (cpu_arch == "mipsel") {
+    android_prebuilt_arch = "android-mips"
+    _binary_prefix = "mipsel-linux-android"
     android_toolchain_root = "$mips_android_toolchain_root"
     android_libgcc_file =
       "$android_toolchain_root/lib/gcc/mipsel-linux-android/${_android_toolchain_version}/libgcc.a"
@@ -102,6 +108,9 @@ if (is_android) {
     assert(false, "Need android libgcc support for your target arch.")
   }
 
+  android_readelf = "$android_toolchain_root/bin/$_binary_prefix-readelf"
+  android_gdbserver = "$android_ndk_root/prebuilt/$android_prebuilt_arch/gdbserver/gdbserver"
+
   # stlport stuff --------------------------------------------------------------
 
   use_system_stlport = is_android_webview_build