Index: cmake/modules/LLVMExternalProjectUtils.cmake
===================================================================
--- cmake/modules/LLVMExternalProjectUtils.cmake
+++ cmake/modules/LLVMExternalProjectUtils.cmake
@@ -149,6 +149,7 @@
                -DPACKAGE_VERSION=${PACKAGE_VERSION}
                -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
                -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
+               -DCMAKE_EXPORT_COMPILE_COMMANDS=1
                ${ARG_CMAKE_ARGS}
                ${PASSTHROUGH_VARIABLES}
     INSTALL_COMMAND ""