CRASH (8.0.0) Travis MacOS build failing due to OOM

MacOS build on Travis is failing: https://travis-ci.com/github/DynamoRIO/dynamorio/jobs/356471150. There seems to be some OOM issue causing malloc to fail.

DR Version: 8.0.18439. Latest build using HEAD also fails. OS: OSX; macOS 10.14.6; osx_image: xcode11.3; Xcode version: Xcode 11.3.1 64 bit build

The failure seems to appear between #4339 and #4342, so it's not caused by us.