cmake: Always pass through stdout/stderr in --build mode

Enable the --use-stderr behavior by default and ignore the old option.
Passing through the pipes allows color terminal output and other things
to work as if one ran the native build command directly.

Help/manual/cmake.1.rst

@@ -64,10 +64,7 @@ native tool on their platform.
     --config <cfg> = For multi-configuration tools, choose <cfg>.
     --clean-first  = Build target 'clean' first, then build.
                      (To clean only, use --target 'clean'.)
-    --use-stderr   = Don't merge stdout/stderr output and pass the
+    --use-stderr   = Ignored.  Behavior is default in CMake >= 3.0.
-                     original stdout/stderr handles to the native
-                     tool so it can use the capabilities of the
-                     calling terminal (e.g. colored output).
     --             = Pass remaining options to the native tool.
 
   Run cmake --build with no options for quick help.

Source/cmake.cxx

@@ -2875,8 +2875,7 @@ int cmake::Build(const std::string& dir,
                  const std::string& target,
                  const std::string& config,
                  const std::vector<std::string>& nativeOptions,
-                 bool clean,
+                 bool clean)
-                 cmSystemTools::OutputOption outputflag)
 {
   if(!cmSystemTools::FileIsDirectory(dir.c_str()))
     {
@@ -2918,7 +2917,8 @@ int cmake::Build(const std::string& dir,
                     projName.c_str(), target.c_str(),
                     &output,
                     makeProgram.c_str(),
-                    config.c_str(), clean, false, 0, outputflag,
+                    config.c_str(), clean, false, 0,
+                    cmSystemTools::OUTPUT_PASSTHROUGH,
                     0, nativeOptions);
 }
 

Source/cmake.h

@@ -362,8 +362,7 @@ class cmake
             const std::string& target,
             const std::string& config,
             const std::vector<std::string>& nativeOptions,
-            bool clean,
+            bool clean);
-            cmSystemTools::OutputOption outputflag);
 
   void UnwatchUnusedCli(const char* var);
   void WatchUnusedCli(const char* var);

Source/cmakemain.cxx

@@ -50,10 +50,7 @@ static const char * cmDocumentationUsage[][2] =
   "  --config <cfg> = For multi-configuration tools, choose <cfg>.\n"   \
   "  --clean-first  = Build target 'clean' first, then build.\n"        \
   "                   (To clean only, use --target 'clean'.)\n"         \
-  "  --use-stderr   = Don't merge stdout/stderr output and pass the\n"  \
+  "  --use-stderr   = Ignored.  Behavior is default in CMake >= 3.0.\n" \
-  "                   original stdout/stderr handles to the native\n"   \
-  "                   tool so it can use the capabilities of the\n"     \
-  "                   calling terminal (e.g. colored output).\n"        \
   "  --             = Pass remaining options to the native tool.\n"
 
 //----------------------------------------------------------------------------
@@ -372,7 +369,6 @@ static int do_build(int ac, char** av)
   std::string dir;
   std::vector<std::string> nativeOptions;
   bool clean = false;
-  cmSystemTools::OutputOption outputflag = cmSystemTools::OUTPUT_MERGE;
 
   enum Doing { DoingNone, DoingDir, DoingTarget, DoingConfig, DoingNative};
   Doing doing = DoingDir;
@@ -397,7 +393,7 @@ static int do_build(int ac, char** av)
       }
     else if(strcmp(av[i], "--use-stderr") == 0)
       {
-      outputflag = cmSystemTools::OUTPUT_PASSTHROUGH;
+      /* tolerate legacy option */
       }
     else if(strcmp(av[i], "--") == 0)
       {
@@ -444,6 +440,6 @@ static int do_build(int ac, char** av)
     }
 
   cmake cm;
-  return cm.Build(dir, target, config, nativeOptions, clean, outputflag);
+  return cm.Build(dir, target, config, nativeOptions, clean);
 #endif
 }