Build object library targets in Makefiles

Treat OBJECT libraries as STATIC libraries but leave out the archive
step.  The object files will be left behind for reference by other
targets later.

Source/cmMakefileLibraryTargetGenerator.cxx

@@ -101,6 +101,9 @@ void cmMakefileLibraryTargetGenerator::WriteRuleFiles()
         this->WriteModuleLibraryRules(true);
         }
       break;
+    case cmTarget::OBJECT_LIBRARY:
+      this->WriteObjectLibraryRules();
+      break;
     default:
       // If language is not known, this is an error.
       cmSystemTools::Error("Unknown Library Type");
@@ -121,6 +124,29 @@ void cmMakefileLibraryTargetGenerator::WriteRuleFiles()
   this->CloseFileStreams();
 }
 
+//----------------------------------------------------------------------------
+void cmMakefileLibraryTargetGenerator::WriteObjectLibraryRules()
+{
+  std::vector<std::string> commands;
+  std::vector<std::string> depends;
+
+  // Add post-build rules.
+  this->LocalGenerator->
+    AppendCustomCommands(commands, this->Target->GetPostBuildCommands(),
+                         this->Target);
+
+  // Depend on the object files.
+  this->AppendObjectDepends(depends);
+
+  // Write the rule.
+  this->LocalGenerator->WriteMakeRule(*this->BuildFileStream, 0,
+                                      this->Target->GetName(),
+                                      depends, commands, true);
+
+  // Write the main driver rule to build everything in this target.
+  this->WriteTargetDriverRule(this->Target->GetName(), false);
+}
+
 //----------------------------------------------------------------------------
 void cmMakefileLibraryTargetGenerator::WriteStaticLibraryRules()
 {