Ninja: depend on language module information files directly

Now that `GetLinkedTargetDirectories` can get the exact dependencies,
use them to simplify the collation dependency graph.

Source/cmNinjaTargetGenerator.cxx

@@ -1146,6 +1146,11 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatements(
 
     cmNinjaBuild build(this->LanguageDyndepRule(language, config));
     build.Outputs.push_back(this->GetDyndepFilePath(language, config));
+    build.ImplicitOuts.push_back(
+      cmStrCat(this->Makefile->GetCurrentBinaryDirectory(), '/',
+               this->LocalGenerator->GetTargetDirectory(this->GeneratorTarget),
+               this->GetGlobalGenerator()->ConfigDirectory(config), '/',
+               language, "Modules.json"));
     for (auto const& scanFiles : scanningFiles) {
       if (!scanFiles.ScanningOutput.empty()) {
         build.ExplicitDeps.push_back(scanFiles.ScanningOutput);
@@ -1157,17 +1162,10 @@ void cmNinjaTargetGenerator::WriteObjectBuildStatements(
 
     this->WriteTargetDependInfo(language, config);
 
-    // Make sure dyndep files for all our dependencies have already
-    // been generated so that the '<LANG>Modules.json' files they
-    // produced as side-effects are available for us to read.
-    // Ideally we should depend on the '<LANG>Modules.json' files
-    // from our dependencies directly, but we don't know which of
-    // our dependencies produces them.  Fixing this will require
-    // refactoring the Ninja generator to generate targets in
-    // dependency order so that we can collect the needed information.
-    this->GetLocalGenerator()->AppendTargetDepends(
-      this->GeneratorTarget, build.OrderOnlyDeps, config, fileConfig,
-      DependOnTargetArtifact);
+    for (std::string const& l :
+         this->GetLinkedTargetDirectories(language, config)) {
+      build.ImplicitDeps.push_back(cmStrCat(l, '/', language, "Modules.json"));
+    }
 
     this->GetGlobalGenerator()->WriteBuild(this->GetImplFileStream(fileConfig),
                                            build);