diff --git a/clang/CMakeLists.txt b/clang/CMakeLists.txt
--- a/clang/CMakeLists.txt
+++ b/clang/CMakeLists.txt
@@ -94,10 +94,12 @@
     endif()
 
     # Seek installed Lit.
-    find_program(LLVM_LIT
-                 NAMES llvm-lit lit.py lit
-                 PATHS "${LLVM_MAIN_SRC_DIR}/utils/lit"
-                 DOC "Path to lit.py")
+    if (NOT LLVM_EXTERNAL_LIT)
+      find_program(LLVM_EXTERNAL_LIT
+                   NAMES llvm-lit lit.py lit
+                   PATHS "${LLVM_MAIN_SRC_DIR}/utils/lit"
+                   DOC "Path to lit.py")
+    endif()
 
     if(EXISTS ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
       # Note: path not really used, except for checking if lit was found
@@ -119,7 +121,7 @@
       endif()
     endif()
 
-    if(LLVM_LIT)
+    if(LLVM_EXTERNAL_LIT)
       # Define the default arguments to use with 'lit', and an option for the user
       # to override.
       set(LIT_ARGS_DEFAULT "-sv")