642f754219
Bug was introduced by 91bc8005fe.
- Move the Dart stack pointer from R19 (C preserved) to R15 (C volatile) so it isn't among the registers saved by the InvokeDartCode stub.
- Set a default cross compiler for ARM64.
- Use ARM32 instead of IA32 binary to build Observatory on ARM64 hosts.
R=regis@google.com
Review URL: https://codereview.chromium.org/1559223003 .