build: stage movement for dispatch build output

In order to support libdispatch tests on Windows, the build tree layout needs to
be adjusted.  Account for this path adjustment here in a compatible manner.

Author: compnerd

Utilities/bootstrap

@@ -261,6 +261,7 @@ class Target(object):
             other_args.extend(["-Xcc", "-F" + args.foundation_path])
             import_paths.append(os.path.join(args.foundation_path, "swift"))
         if args.libdispatch_build_dir:
+            import_paths.append(os.path.join(args.libdispatch_build_dir, 'lib'))
             import_paths.append(os.path.join(args.libdispatch_build_dir, "src"))
             import_paths.append(os.path.join(args.libdispatch_build_dir, "src", "swift"))
         if args.libdispatch_source_dir:
@@ -579,8 +580,10 @@ class llbuild(object):
                     link_command.extend(["-L", self.args.foundation_path])
                 if self.args.libdispatch_build_dir:
                     link_command.extend(['-L', self.args.libdispatch_build_dir,
+                                         '-L', os.path.join(self.args.libdispatch_build_dir, 'lib'),
                                          '-Xlinker', '-lBlocksRuntime'])
-                    link_command.extend(["-L", os.path.join(self.args.libdispatch_build_dir, "src")])
+                    link_command.extend(['-L', os.path.join(self.args.libdispatch_build_dir, "src"),
+                                         '-L', os.path.join(self.args.libdispatch_build_dir, 'lib')])
 
                 # Add llbuild link flags.
                 link_command.extend(llbuild_link_args(self.args))