--- a/build/build-clang/build-clang.py
+++ b/build/build-clang/build-clang.py
@@ -200,16 +200,18 @@ def build_one_stage(cc, cxx, ld, ar, ran
     build_dir = stage_dir + "/build"
     inst_dir = stage_dir + "/clang"
 
     # If CMake has already been run, it may have been run with different
     # arguments, so we need to re-run it.  Make sure the cached copy of the
     # previous CMake run is cleared before running it again.
     if os.path.exists(build_dir + "/CMakeCache.txt"):
         os.remove(build_dir + "/CMakeCache.txt")
+    if os.path.exists(build_dir + "/CMakeFiles"):
+        shutil.rmtree(build_dir + "/CMakeFiles")
 
     # cmake doesn't deal well with backslashes in paths.
     def slashify_path(path):
         return path.replace('\\', '/')
 
     cmake_args = ["-GNinja",
                   "-DCMAKE_C_COMPILER=%s" % slashify_path(cc[0]),
                   "-DCMAKE_CXX_COMPILER=%s" % slashify_path(cxx[0]),