Merge topic 'make-clean-no-targets'

81bc7610ab Makefile: Fix "make clean" when there are no targets

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !1833

Source/cmGlobalUnixMakefileGenerator3.cxx

@@ -241,6 +241,10 @@ void cmGlobalUnixMakefileGenerator3::WriteMainMakefile2()
   lg->WriteMakeRule(makefileStream, "The main recursive preinstall target",
                     "preinstall", depends, no_commands, true);
 
+  // Write an empty clean:
+  lg->WriteMakeRule(makefileStream, "The main recursive clean target", "clean",
+                    depends, no_commands, true);
+
   // Write out the "special" stuff
   lg->WriteSpecialTargetsTop(makefileStream);