Source: Add cm_fileno wrapper

And use it where appropriate.

Source/CMakeLists.txt

@@ -738,6 +738,8 @@ add_library(
   cm_utf8.c
   cm_codecvt.hxx
   cm_codecvt.cxx
+  cm_fileno.hxx
+  cm_fileno.cxx
 
   cmDuration.h
   cmDuration.cxx

Source/cm_fileno.cxx

@@ -0,0 +1,15 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#if !defined(_POSIX_C_SOURCE) && !defined(_WIN32) && !defined(__sun) &&       \
+  !defined(__OpenBSD__)
+/* POSIX APIs are needed */
+// NOLINTNEXTLINE(bugprone-reserved-identifier)
+#  define _POSIX_C_SOURCE 200809L
+#endif
+
+#include "cm_fileno.hxx"
+
+int cm_fileno(FILE* f)
+{
+  return fileno(f);
+}

Source/cm_fileno.hxx

@@ -0,0 +1,7 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file Copyright.txt or https://cmake.org/licensing for details.  */
+#pragma once
+
+#include <cstdio>
+
+int cm_fileno(FILE* f);

Source/cmake.cxx

@@ -23,14 +23,11 @@
 #include <cmext/algorithm>
 #include <cmext/string_view>
 
-#if !defined(CMAKE_BOOTSTRAP) && !defined(_WIN32)
-#  include <unistd.h>
-#endif
-
 #include "cmsys/FStream.hxx"
 #include "cmsys/Glob.hxx"
 #include "cmsys/RegularExpression.hxx"
 
+#include "cm_fileno.hxx"
 #include "cm_sys_stat.h"
 
 #include "cmBuildOptions.h"
@@ -3913,15 +3910,11 @@ std::function<int()> cmake::BuildWorkflowStep(
   const std::vector<std::string>& args)
 {
   cmUVProcessChainBuilder builder;
-  builder
-    .AddCommand(args)
-#  ifdef _WIN32
-    .SetExternalStream(cmUVProcessChainBuilder::Stream_OUTPUT, _fileno(stdout))
-    .SetExternalStream(cmUVProcessChainBuilder::Stream_ERROR, _fileno(stderr));
-#  else
-    .SetExternalStream(cmUVProcessChainBuilder::Stream_OUTPUT, STDOUT_FILENO)
-    .SetExternalStream(cmUVProcessChainBuilder::Stream_ERROR, STDERR_FILENO);
-#  endif
+  builder.AddCommand(args)
+    .SetExternalStream(cmUVProcessChainBuilder::Stream_OUTPUT,
+                       cm_fileno(stdout))
+    .SetExternalStream(cmUVProcessChainBuilder::Stream_ERROR,
+                       cm_fileno(stderr));
   return [builder]() -> int {
     auto chain = builder.Start();
     chain.Wait();