[build] Don't download Android NDK and tools by default.

Saves 2.3GB for most builders. The Android builders already set the gclient variable download_android_deps to True.

Cq-Include-Trybots: luci.dart.try:vm-aot-android-release-arm64c-try,vm-aot-android-release-arm_x64-try,vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64c-try,vm-ffi-android-product-arm-try,vm-ffi-android-product-arm64c-try,vm-ffi-android-release-arm-try,vm-ffi-android-release-arm64c-try
Change-Id: Ib536d8d937d9a37ca46b32db213ac75d9d3bc9b7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/429560
Reviewed-by: Alexander Aprelev <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>

Author: rmacnak-google

DEPS

@@ -64,8 +64,7 @@ vars = {
   "checkout_flute": False,
 
   # Checkout Android dependencies only on Mac and Linux.
-  "download_android_deps":
-    "host_os == mac or (host_os == linux and host_cpu == x64)",
+  "download_android_deps": False,
 
   # Checkout extra javascript engines for testing or benchmarking. You can
   # self-service update these by following the go/dart-engprod/browsers.md