FreeBSD: TSan: Disable Race condition tests

There are a couple of known race conditions that seem to be stemming
from the concurrency runtime, triggering test failures in the TSan
tests.

rdar://158355890

Author: etcwilde

test/Sanitizers/tsan/async_taskgroup_next.swift

@@ -10,6 +10,9 @@
 // Thread destruction interceptor marks the thread ignored and then checks that
 // the thread isn't being ignored.
 // rdar://158450231
+// TSan is also occasionally detecting race conditions in the concurrency
+// runtime on FreeBSD.
+// rdar://158355890
 // XFAIL: OS=freebsd
 
 var scratchBuffer: UnsafeMutableBufferPointer<Int> = .allocate(capacity: 1000)

test/Sanitizers/tsan/once.swift

@@ -17,6 +17,12 @@
 // on some platforms TSan wasn't seeing the synchronization, so would report
 // a false positive.
 
+// TSan is detecting race conditions in the concurrency runtime.
+// This might be an issue in how it is hooked into the underlying threading
+// model on FreeBSD.
+// rdar://158355890
+// XFAIL: OS=freebsd
+
 import Dispatch
 
 var count = 0

test/Sanitizers/tsan/tsan.swift

@@ -14,6 +14,12 @@
 // don't support TSan.
 // UNSUPPORTED: remote_run
 
+// TSan is detecting race conditions in the concurrency runtime.
+// This might be an issue in how it is hooked into the underlying threading
+// model on FreeBSD.
+// rdar://158355890
+// XFAIL: OS=freebsd
+
 #if canImport(Darwin)
   import Darwin
 #elseif canImport(Glibc)