[scudo][standalone] Make malloc_info return a minimal XML

Initially, our malloc_info was returning ENOTSUP, but Android would
rather have it return successfully and write a barebone XML to the
stream, so we will oblige.

Add an associated test.

Reviewers: cferris, morehouse, hctim, eugenis, vitalybuka

Reviewed By: morehouse

Subscribers: delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D68427

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@373754 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed