[libc++] Adjust how we guard the inclusion of unistd.h
unistd.h isn't guaranteed to exist when the target isn't Windows, in
particular if the target is bare-metal (i.e. no operating system).
Handle this by using __has_include instead, though in
filesystem/operations.cpp we already unconditionally include it so
just remove the extra include.
Differential Revision: https://reviews.llvm.org/D79784
Cr-Mirrored-From: https://chromium.googlesource.com/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 4d25f4453d60dee522e905c844dde0f4b6ed9475
diff --git a/src/chrono.cpp b/src/chrono.cpp
index 48c02c8..a1a456f 100644
--- a/src/chrono.cpp
+++ b/src/chrono.cpp
@@ -12,7 +12,7 @@
#include <time.h> // clock_gettime, CLOCK_MONOTONIC and CLOCK_REALTIME
#include "include/apple_availability.h"
-#if !defined(_WIN32)
+#if __has_include(<unistd.h>)
#include <unistd.h>
#endif