Temporarily disable sanitizers tests on Linux, as recent kernel updat…

[cheshire]

…e breaks them.

Cf. google/sanitizers#837
Tracked in https://bugs.swift.org/browse/SR-6257

[cheshire]

@swift-ci please smoke test and merge

[DougGregor]

FYI:

home/buildnode/jenkins/workspace/swift-PR-Linux-smoke-test/branch-master/buildbot_linux/swift-linux-x86_64/bin/swift-autolink-extract
lit.py: /home/buildnode/jenkins/workspace/swift-PR-Linux-smoke-test/branch-master/llvm/utils/lit/lit/TestingConfig.py:101: fatal: unable to parse config file '/home/buildnode/jenkins/workspace/swift-PR-Linux-smoke-test/branch-master/swift/test/lit.cfg', traceback: Traceback (most recent call last):
File "/home/buildnode/jenkins/workspace/swift-PR-Linux-smoke-test/branch-master/llvm/utils/lit/lit/TestingConfig.py", line 88, in load_from_path
exec(compile(data, path, 'exec'), cfg_globals, None)
File "/home/buildnode/jenkins/workspace/swift-PR-Linux-smoke-test/branch-master/swift/test/lit.cfg", line 941, in
runtime_libs['tsan'] = 'tsan_runtime'
TypeError: list indices must be integers, not strings

[cheshire]

@swift-ci please smoke test