Makefile: Always create clean target command

Borland Make complains if the phony clean target has no rule to build it.
If there are no files to clean, generate and run an empty clean script.

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -1158,27 +1158,25 @@ cmLocalUnixMakefileGenerator3
                      const std::vector<std::string>& files,
                      cmTarget& target, const char* filename)
 {
+  std::string cleanfile = this->Makefile->GetCurrentOutputDirectory();
+  cleanfile += "/";
+  cleanfile += this->GetTargetDirectory(target);
+  cleanfile += "/cmake_clean";
+  if(filename)
+    {
+    cleanfile += "_";
+    cleanfile += filename;
+    }
+  cleanfile += ".cmake";
+  std::string cleanfilePath = this->Convert(cleanfile.c_str(), FULL);
+  std::ofstream fout(cleanfilePath.c_str());
+  if(!fout)
+    {
+    cmSystemTools::Error("Could not create ", cleanfilePath.c_str());
+    }
   if(!files.empty())
     {
-    std::string cleanfile = this->Makefile->GetCurrentOutputDirectory();
-    cleanfile += "/";
-    cleanfile += this->GetTargetDirectory(target);
-    cleanfile += "/cmake_clean";
-    if(filename)
-      {
-      cleanfile += "_";
-      cleanfile += filename;
-      }
-    cleanfile += ".cmake";
-    std::string cleanfilePath = this->Convert(cleanfile.c_str(), FULL);
-    std::ofstream fout(cleanfilePath.c_str());
-    if(!fout)
-      {
-      cmSystemTools::Error("Could not create ", cleanfilePath.c_str());
-      }
     fout << "file(REMOVE_RECURSE\n";
-    std::string remove = "$(CMAKE_COMMAND) -P ";
-    remove += this->Convert(cleanfile.c_str(), START_OUTPUT, SHELL);
     for(std::vector<std::string>::const_iterator f = files.begin();
         f != files.end(); ++f)
       {
@@ -1186,27 +1184,29 @@ cmLocalUnixMakefileGenerator3
       fout << "  " << this->EscapeForCMake(fc.c_str()) << "\n";
       }
     fout << ")\n";
-    commands.push_back(remove);
-
-    // For the main clean rule add per-language cleaning.
-    if(!filename)
+    }
+  std::string remove = "$(CMAKE_COMMAND) -P ";
+  remove += this->Convert(cleanfile.c_str(), START_OUTPUT, SHELL);
+  commands.push_back(remove);
+
+  // For the main clean rule add per-language cleaning.
+  if(!filename)
+    {
+    // Get the set of source languages in the target.
+    std::set<cmStdString> languages;
+    target.GetLanguages(languages);
+    fout << "\n"
+         << "# Per-language clean rules from dependency scanning.\n"
+         << "foreach(lang";
+    for(std::set<cmStdString>::const_iterator l = languages.begin();
+        l != languages.end(); ++l)
       {
-      // Get the set of source languages in the target.
-      std::set<cmStdString> languages;
-      target.GetLanguages(languages);
-      fout << "\n"
-           << "# Per-language clean rules from dependency scanning.\n"
-           << "foreach(lang";
-      for(std::set<cmStdString>::const_iterator l = languages.begin();
-          l != languages.end(); ++l)
-        {
-        fout << " " << *l;
-        }
-      fout << ")\n"
-           << "  include(" << this->GetTargetDirectory(target)
-           << "/cmake_clean_${lang}.cmake OPTIONAL)\n"
-           << "endforeach()\n";
+      fout << " " << *l;
       }
+    fout << ")\n"
+         << "  include(" << this->GetTargetDirectory(target)
+         << "/cmake_clean_${lang}.cmake OPTIONAL)\n"
+         << "endforeach()\n";
     }
 }