Mark test using <sys/time.h> as UNSUPPORTED on Windows

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@302298 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp

@@ -9,6 +9,9 @@
 //
 // UNSUPPORTED: libcpp-has-no-threads
 
+// This test uses the POSIX header <sys/time.h> which Windows doesn't provide
+// UNSUPPORTED: windows
+
 // This test depends on signal behaviour until r210210, so some system libs
 // don't pass.
 //