[scudo] Use the macro get_test_cc_for_arch for the tests

Summary: The macro was introduced with D26929, use it in Scudo as well.

Reviewers: kcc, alekseyshl, kubabrecka

Subscribers: llvm-commits, danalbert, srhines, mgorny

Differential Revision: https://reviews.llvm.org/D28066

llvm-svn: 290439