Removed raw references to __APPLE__; now just check to see if it is defined.

llvm-svn: 177297
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: b56e8587aff9d8766a673f51b2d9c525e1535d84
diff --git a/src/chrono.cpp b/src/chrono.cpp
index 1ce2e28..15a6f46 100644
--- a/src/chrono.cpp
+++ b/src/chrono.cpp
@@ -9,7 +9,7 @@
 
 #include "chrono"
 #include <sys/time.h>        //for gettimeofday and timeval
-#if __APPLE__
+#ifdef __APPLE__
 #include <mach/mach_time.h>  // mach_absolute_time, mach_timebase_info_data_t
 #else  /* !__APPLE__ */
 #include <cerrno>  // errno
@@ -50,7 +50,7 @@
 
 const bool steady_clock::is_steady;
 
-#if __APPLE__
+#ifdef __APPLE__
 //   mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
 //   nanoseconds since the computer booted up.  MachInfo.numer and MachInfo.denom
 //   are run time constants supplied by the OS.  This clock has no relationship