main.mk: Set dalvik.vm.stack-trace-dir

... instead of dalvik.vm.stack-trace-file. Turns on the new
stack dumping scheme. Each dump is now output to a separate file.

Bug: 32064548
Test: Manual, unit tests included in other components.
Change-Id: I762b09148786e8533fd285d5bae0121ed46dfbe0
1 file changed