Update checked-in SDKs to 2.0.0-dev.47.0

Update the README to say that linux and macos use the 64-bit SDK
and windows uses the 32-bit SDK.

Change-Id: Id98d6aa49ed0a486aa8553b4d08f76a2462fb6b7
Reviewed-on: https://dart-review.googlesource.com/50503
Commit-Queue: William Hesse <whesse@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>

Author: whesse

tools/sdks/README

@@ -11,10 +11,8 @@ the download script is hardcoded to recognize.
 The linux SDK has two extra dart executables added to the bin directory.
 'dart-arm' and 'dart-arm64' are executables compiled to run on
 arm and arm64 (aarch64) processors, respectively. We are currently
-using the 32-bit ia32 build as the default on linux, windows, and macos.
-If we switch to the 64-bit build on linux, the snapshots will no longer be
-portable to arm and arm64, and we will need to upload complete SDKs for each
-processor architecture.
+using the 32-bit ia32 build as the default on windows, and the 64-bit x64
+build as the default on linux and macos.
 
 To upload new versions of these tar files, use the "upload_to_google_storage"
 tool in depot_tools, and download the new stable SDKs from the dartlang.org

tools/sdks/linux/dart-sdk.tar.gz.sha1

@@ -1 +1 @@
-d603d2f9fe59281e37a250cb3105ab54d1c25e64
+2bb209191a1e2928b322636727c681cc0c3cf825

tools/sdks/mac/dart-sdk.tar.gz.sha1

@@ -1 +1 @@
-7b5adc71c75dc07815ccd8f233c4ccf50d11e11f
+32908822cad77ec2ea148440cc6f99d172f477dc

tools/sdks/win/dart-sdk.tar.gz.sha1

@@ -1 +1 @@
-520e55c06f22a50938c1682e6e0a56161fc43a65
+e8959966bba1424ac2573d15caff499281cb7d87