[Support/Unix] Unconditionally include time.h.

When building LLVM on Linux with libc++ with CMake TIME_WITH_SYS_TIME is
undefined, and HAVE_SYS_TIME_H is defined. This ends up including
sys/time.h but not time.h. Unix/TimeValue.inc requires time.h for asctime_r
and localtime. libstdc++ seems to include time.h anyway, but libc++ does
not.

Fix this by always including time.h

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155382 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Unix/Unix.h b/lib/Support/Unix/Unix.h
index b7be311..361f297 100644
--- a/lib/Support/Unix/Unix.h
+++ b/lib/Support/Unix/Unix.h
@@ -44,16 +44,10 @@
 #include <assert.h>
 #endif
 
-#ifdef TIME_WITH_SYS_TIME
+#ifdef HAVE_SYS_TIME_H
 # include <sys/time.h>
-# include <time.h>
-#else
-# ifdef HAVE_SYS_TIME_H
-#  include <sys/time.h>
-# else
-#  include <time.h>
-# endif
 #endif
+#include <time.h>
 
 #ifdef HAVE_SYS_WAIT_H
 # include <sys/wait.h>