If the "build_lib" command built any C libraries, link with them all

  when building extensions (uses build_lib's 'get_library_names()' method).
Ensure that the relative structure of source filenames is preserved in
  the temporary build tree, eg. foo/bar.c compiles to
  build/temp.<plat>/foo/bar.o.

command/build_ext.py

@@ -164,7 +164,15 @@ class build_ext (Command):
             self.compiler.set_runtime_library_dirs (self.rpath)
         if self.link_objects is not None:
             self.compiler.set_link_objects (self.link_objects)
-                                      
+
+        if self.distribution.libraries:
+            build_lib = self.find_peer ('build_lib')
+            self.libraries = build_lib.get_library_names () or []
+            self.library_dirs = [build_lib.build_clib]
+        else:
+            self.libraries = []
+            self.library_dirs = []
+
         # Now the real loop over extensions
         self.build_extensions (self.extensions)
 
@@ -237,6 +245,7 @@ class build_ext (Command):
             include_dirs = build_info.get ('include_dirs')
             objects = self.compiler.compile (sources,
                                              output_dir=self.build_temp,
+                                             keep_dir=1,
                                              macros=macros,
                                              include_dirs=include_dirs,
                                              debug=self.debug)
@@ -247,8 +256,8 @@ class build_ext (Command):
             extra_objects = build_info.get ('extra_objects')
             if extra_objects:
                 objects.extend (extra_objects)
-            libraries = build_info.get ('libraries')
-            library_dirs = build_info.get ('library_dirs')
+            libraries = self.libraries + build_info.get ('libraries')
+            library_dirs = self.library_dirs + build_info.get ('library_dirs')
             extra_args = build_info.get ('extra_link_args') or []
 
             if self.compiler.compiler_type == 'msvc':