Merge branch 'backport-ninja-issue-17942' into ninja-issue-17942

Source/cmGeneratorExpressionEvaluationFile.cxx

@@ -105,8 +105,14 @@ void cmGeneratorExpressionEvaluationFile::CreateOutputFile(
       lg, config, false, nullptr, nullptr, nullptr, le);
     cmSourceFile* sf = lg->GetMakefile()->GetOrCreateSource(
       name, false, cmSourceFileLocationKind::Known);
+    // Tell TraceDependencies that the file is not expected to exist
+    // on disk yet.  We generate it after that runs.
     sf->SetProperty("GENERATED", "1");
 
+    // Tell the build system generators that there is no build rule
+    // to generate the file.
+    sf->SetProperty("__CMAKE_GENERATED_BY_CMAKE", "1");
+
     gg->SetFilenameTargetDepends(
       sf, this->OutputFileExpr->GetSourceSensitiveTargets());
   }

Source/cmNinjaTargetGenerator.cxx

@@ -948,7 +948,9 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatement(
   // (either attached to this source file or another one), assume that one of
   // the target dependencies, OBJECT_DEPENDS or header file custom commands
   // will rebuild the file.
-  if (source->GetPropertyAsBool("GENERATED") && !source->GetCustomCommand() &&
+  if (source->GetPropertyAsBool("GENERATED") &&
+      !source->GetPropertyAsBool("__CMAKE_GENERATED_BY_CMAKE") &&
+      !source->GetCustomCommand() &&
       !this->GetGlobalGenerator()->HasCustomCommandOutput(sourceFileName)) {
     this->GetGlobalGenerator()->AddAssumedSourceDependencies(sourceFileName,
                                                              orderOnlyDeps);