Precompile headers: Add support for Xcode generator

Co-Author: Daniel Pfeifer <[email protected]>

Source/cmGlobalXCodeGenerator.cxx

@@ -2374,6 +2374,16 @@ void cmGlobalXCodeGenerator::CreateBuildSettings(cmGeneratorTarget* gtgt,
     buildSettings->AddAttribute("DYLIB_COMPATIBILITY_VERSION",
                                 this->CreateString(vso.str()));
   }
+
+  // Precompile Headers
+  std::string pchHeader = gtgt->GetPchHeader(configName, llang);
+  if (!pchHeader.empty()) {
+    buildSettings->AddAttribute("GCC_PREFIX_HEADER",
+                                this->CreateString(pchHeader));
+    buildSettings->AddAttribute("GCC_PRECOMPILE_PREFIX_HEADER",
+                                this->CreateString("YES"));
+  }
+
   // put this last so it can override existing settings
   // Convert "XCODE_ATTRIBUTE_*" properties directly.
   {
@@ -2829,6 +2839,8 @@ bool cmGlobalXCodeGenerator::CreateGroups(
         continue;
       }
 
+      generator->AddPchDependencies(gtgt, "");
+
       auto addSourceToGroup = [this, mf, gtgt,
                                &sourceGroups](std::string const& source) {
         cmSourceGroup* sourceGroup = mf->FindSourceGroup(source, sourceGroups);