[libc++] Flag file_clock test as expected to fail with ASAN

This silences a known issue, as can be seen by looking at similar
tests for other clocks, like time.clock.steady/consistency.pass.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@356528 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp b/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp
index 585433a..34244a8 100644
--- a/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp
+++ b/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp
@@ -8,6 +8,10 @@
 //
 // UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
 
+// Due to C++17 inline variables ASAN flags this test as containing an ODR
+// violation because Clock::is_steady is defined in both the dylib and this TU.
+// UNSUPPORTED: asan
+
 // <chrono>
 
 // file_clock