diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -483,12 +483,6 @@
     # when building tests) to allow enabling filesystem for running tests,
     # even if it uses a non-permanent ABI.
 
-    # TODO: The CI runner currently uses Clang 11, which doesn't implicitly
-    # link in oldnames.lib (which is needed for some tests) when compiling
-    # with the plain "clang" driver, as the tests do (as opposed to using
-    # the "clang-cl" driver for compiling). When the CI runner runs
-    # Clang 12, the "-loldnames" option can be dropped.
-
     # TODO: Currently, building with the experimental library breaks running
     # tests (the test linking look for the c++experimental library with the
     # wrong name, and the statically linked c++experimental can't be linked
@@ -507,8 +501,7 @@
           -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=NO \
           -DLIBCXX_ENABLE_FILESYSTEM=YES \
           -DCMAKE_CXX_FLAGS="-D_LIBCPP_HAS_NO_INT128" \
-          -DLIBCXX_TEST_COMPILER_FLAGS="-D_LIBCPP_HAS_NO_INT128" \
-          -DLIBCXX_TEST_LINKER_FLAGS="-loldnames"
+          -DLIBCXX_TEST_COMPILER_FLAGS="-D_LIBCPP_HAS_NO_INT128"
     echo "+++ Running the libc++ tests"
     ${NINJA} -vC "${BUILD_DIR}" check-cxx
 ;;
diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -465,6 +465,9 @@
             # libcxx CMakeLists.txt if building targeting msvc.
             self.cxx.link_flags += ['-l%s%s' % (lib, debug_suffix) for lib in
                                     ['vcruntime', 'ucrt', 'msvcrt', 'msvcprt']]
+            # The compiler normally links in oldnames.lib too, but we've
+            # specified -nostdlib above, so we need to specify it manually.
+            self.cxx.link_flags += ['-loldnames']
         elif cxx_abi == 'none' or cxx_abi == 'default':
             if self.target_info.is_windows():
                 debug_suffix = 'd' if self.debug_build else ''