bootstrap: check the new Foundation layout

Ensure that we check the new Foundation location for the paths to the
libraries.

Author: compnerd

Utilities/bootstrap

@@ -586,7 +586,10 @@ class llbuild(object):
                     link_command.extend(
                         ["-Xlinker", "-rpath=$ORIGIN/../lib/swift/linux"])
                 if self.args.foundation_path:
-                    link_command.extend(["-L", self.args.foundation_path])
+                    link_command.extend([
+                        "-L", self.args.foundation_path,
+                        "-L", os.path.join(self.args.foundation_path, "Foundation")
+                    ])
                 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'),