[tsan] Add basic ASan and TSan round trip tests.

test/Sanitizers/asan.swift

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+// RUN: %target-swiftc_driver %s -g -sanitize=address -o %t_tsan-binary
+// RUN: not env ASAN_OPTIONS=abort_on_error=0 %target-run %t_tsan-binary 2>&1 | FileCheck %s
+// REQUIRES: executable_test
+// REQUIRES: objc_interop
+// XFAIL: linux
+
+// Test AddressSanitizer execution end-to-end.
+
+var a = UnsafeMutablePointer<Int>(allocatingCapacity: 1)
+a.initialize(with: 5)
+a.deinitialize(count: 1)
+a.deallocateCapacity(1)
+print(a.pointee)
+a.deinitialize(count: 1)
+a.deallocateCapacity(1)
+
+// CHECK: AddressSanitizer: heap-use-after-free

test/Sanitizers/tsan.swift

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+// RUN: %target-swiftc_driver %s -g -sanitize=thread -o %t_tsan-binary
+// RUN: not env TSAN_OPTIONS=abort_on_error=0 %target-run %t_tsan-binary 2>&1 | FileCheck %s
+// REQUIRES: executable_test
+// REQUIRES: objc_interop
+// REQUIRES: CPU=x86_64
+// XFAIL: linux
+
+// Test ThreadSanitizer execution end-to-end.
+
+import Darwin
+var user_interactive_thread: pthread_t? = nil
+var user_interactive_thread2: pthread_t? = nil
+var racey_x: Int;
+
+pthread_create(&user_interactive_thread, nil, { _ in
+    print("pthread ran")
+    racey_x = 5;
+
+    return nil
+}, nil)
+
+pthread_create(&user_interactive_thread2, nil, { _ in
+    print("pthread2 ran")
+    racey_x = 6;
+
+    return nil
+}, nil)
+
+// CHECK: ThreadSanitizer: data race