GN: Use lib.unstripped rather than lib.stripped. Add a toolchain.gni

build/android/BUILD.gn

Index: build/android/BUILD.gn
diff --git a/build/android/BUILD.gn b/build/android/BUILD.gn
index d90ad70abe6437db0e49f26b01f1d1e817c3ad5d..5e97d1a47b484f3ce7e1c9e0aadc5e5d1d93a56b 100644
--- a/build/android/BUILD.gn
+++ b/build/android/BUILD.gn
@@ -30,7 +30,7 @@ action("cpplib_stripped") {
   _strip_bin = "${android_tool_prefix}strip"
   _soname = "libc++_shared.so"
   _input_so = "${android_libcpp_root}/libs/${android_app_abi}/${_soname}"
-  _output_so = "${root_out_dir}/lib.stripped/${_soname}"
+  _output_so = "${root_shlib_dir}/${_soname}"
 
   script = "//build/gn_run_binary.py"
   inputs = [