diff --git a/clang-tools-extra/clangd/test/CMakeLists.txt b/clang-tools-extra/clangd/test/CMakeLists.txt
--- a/clang-tools-extra/clangd/test/CMakeLists.txt
+++ b/clang-tools-extra/clangd/test/CMakeLists.txt
@@ -28,6 +28,16 @@
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg.py
   )
 
+# Copy an empty compile_commands.json to override the compile_commands.json
+# in the top level build directory.  Or if a clangd test involves creating a
+# temporary source file in the build directory and run clangd to check it,
+# it can pick up unrecognizable command options when LLVM is built with
+# another compiler or a different version of Clang.
+configure_file(
+  ${CMAKE_CURRENT_SOURCE_DIR}/compile_commands.json
+  ${CMAKE_CURRENT_BINARY_DIR}/compile_commands.json
+)
+
 add_lit_testsuite(check-clangd "Running the Clangd regression tests"
   # clangd doesn't put unittest configs in test/unit like every other project.
   # Because of that, this needs to pass two folders here, while every other
diff --git a/clang-tools-extra/clangd/test/compile_commands.json b/clang-tools-extra/clangd/test/compile_commands.json
new file mode 100644
--- /dev/null
+++ b/clang-tools-extra/clangd/test/compile_commands.json
@@ -0,0 +1 @@
+[]