[asan] Improvements for asan deactivated mode: disable asan activation for runtime library on Linux, disable malloc checks.

Reviewed in http://reviews.llvm.org/D6265


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@222732 91177308-0d34-0410-b5e6-96231b3b80d8