Scudo tests in compiler-rt/test/scudo are not run

[rorth]

While looking at compiler-rt tests that use -shared-lib*san, I noticed that the Scudo tests in compiler-rt/test/scudo are not built or run, unlike their counterparts in compiler-rt/test/scudo/standalone.

AFAICT this directory lacks a CMakeLists.txt file that would introduce a check-scudo target.