Revert "Xcode: Obey SYSTEM keyword for includes (#15687)"

Revert commit v3.7.0-rc1~266^2 (Xcode: Obey SYSTEM keyword for includes,
2015-08-31).  It worked for C, C++, and Swift but not for GNU Assembly
files for which Xcode has no property to set flags.

Closes: #16449

Source/cmGlobalXCodeGenerator.cxx

@@ -1894,40 +1894,24 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
 
   BuildObjectListOrString dirs(this, this->XcodeVersion >= 30);
   BuildObjectListOrString fdirs(this, this->XcodeVersion >= 30);
+  std::vector<std::string> includes;
+  this->CurrentLocalGenerator->GetIncludeDirectories(includes, gtgt, "C",
+                                                     configName);
   std::set<std::string> emitted;
   emitted.insert("/System/Library/Frameworks");
 
-  if (this->XcodeVersion < 60) {
-    std::vector<std::string> includes;
-    this->CurrentLocalGenerator->GetIncludeDirectories(includes, gtgt, "C",
-                                                       configName);
-    for (std::vector<std::string>::iterator i = includes.begin();
-         i != includes.end(); ++i) {
-      if (this->NameResolvesToFramework(*i)) {
-        std::string frameworkDir = *i;
-        frameworkDir += "/../";
-        frameworkDir = cmSystemTools::CollapseFullPath(frameworkDir);
-        if (emitted.insert(frameworkDir).second) {
-          fdirs.Add(this->XCodeEscapePath(frameworkDir));
-        }
-      } else {
-        std::string incpath = this->XCodeEscapePath(*i);
-        dirs.Add(incpath);
-      }
-    }
-  } else {
-    for (std::set<std::string>::iterator li = languages.begin();
-         li != languages.end(); ++li) {
-      std::vector<std::string> includes;
-      this->CurrentLocalGenerator->GetIncludeDirectories(includes, gtgt, *li,
-                                                         configName);
-      std::string includeFlags = this->CurrentLocalGenerator->GetIncludeFlags(
-        includes, gtgt, *li, true, false, configName);
-
-      std::string& flags = cflags[*li];
-      if (!includeFlags.empty()) {
-        flags += " " + includeFlags;
+  for (std::vector<std::string>::iterator i = includes.begin();
+       i != includes.end(); ++i) {
+    if (this->NameResolvesToFramework(*i)) {
+      std::string frameworkDir = *i;
+      frameworkDir += "/../";
+      frameworkDir = cmSystemTools::CollapseFullPath(frameworkDir);
+      if (emitted.insert(frameworkDir).second) {
+        fdirs.Add(this->XCodeEscapePath(frameworkDir));
       }
+    } else {
+      std::string incpath = this->XCodeEscapePath(*i);
+      dirs.Add(incpath);
     }
   }
   // Add framework search paths needed for linking.

Tests/IncludeDirectories/CMakeLists.txt

@@ -3,9 +3,7 @@ project(IncludeDirectories)
 
 if (((CMAKE_C_COMPILER_ID STREQUAL GNU AND CMAKE_C_COMPILER_VERSION VERSION_GREATER 4.4)
     OR CMAKE_C_COMPILER_ID STREQUAL Clang OR CMAKE_C_COMPILER_ID STREQUAL AppleClang)
-    AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles"
-      OR CMAKE_GENERATOR STREQUAL "Ninja"
-      OR (CMAKE_GENERATOR STREQUAL "Xcode" AND NOT XCODE_VERSION VERSION_LESS 6.0)))
+    AND (CMAKE_GENERATOR STREQUAL "Unix Makefiles" OR CMAKE_GENERATOR STREQUAL "Ninja"))
   include(CheckCXXCompilerFlag)
   check_cxx_compiler_flag(-Wunused-variable run_sys_includes_test)
   if(run_sys_includes_test)

Tests/IncludeDirectories/SystemIncludeDirectories/CMakeLists.txt

@@ -15,17 +15,10 @@ target_include_directories(upstream SYSTEM PUBLIC
 )
 
 add_library(config_specific INTERFACE)
-if(CMAKE_GENERATOR STREQUAL "Xcode")
-  # CMAKE_BUILD_TYPE does not work here for multi-config generators
-  target_include_directories(config_specific SYSTEM INTERFACE
-    "${CMAKE_CURRENT_SOURCE_DIR}/config_specific"
-  )
-else()
-  set(testConfig ${CMAKE_BUILD_TYPE})
-  target_include_directories(config_specific SYSTEM INTERFACE
-    "$<$<CONFIG:${testConfig}>:${CMAKE_CURRENT_SOURCE_DIR}/config_specific>"
-  )
-endif()
+set(testConfig ${CMAKE_BUILD_TYPE})
+target_include_directories(config_specific SYSTEM INTERFACE
+  "$<$<CONFIG:${testConfig}>:${CMAKE_CURRENT_SOURCE_DIR}/config_specific>"
+)
 
 add_library(consumer consumer.cpp)
 target_link_libraries(consumer upstream config_specific)