[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.

llvm-svn: 356528

libcxx/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