[compiler-rt] Disable interception tests on Apple

Summary:
The CMake generation is not working on Apple.

This patch is disabling the generation until it's fixed.

Reviewers: rnk

Subscribers: tberghammer, chrisha, danalbert, llvm-commits, srhines

Differential Revision: http://reviews.llvm.org/D22066

llvm-svn: 274667