[Test-Suite] Fix all the sanitizer tests to be based on compiler capabilities

Summary: This patch reworks all the @skip... lines for sanitizer libraries to be based on whether or not the compiler actually works, rather than whether or not the compiler-rt sources are present in some magically derived directory.

Reviewers: lldb-commits

Subscribers: kubabrecka, tfiala

Differential Revision: https://reviews.llvm.org/D26513

llvm-svn: 286490