diff --git a/lldb/test/CMakeLists.txt b/lldb/test/CMakeLists.txt
--- a/lldb/test/CMakeLists.txt
+++ b/lldb/test/CMakeLists.txt
@@ -106,7 +106,7 @@
     else()
       # We require libcxx for the test suite, so if we aren't building it,
       # try to provide a helpful error about how to resolve the situation.
-      if(NOT TARGET cxx)
+      if(NOT TARGET cxx AND NOT libcxx IN_LIST LLVM_ENABLE_RUNTIMES)
         if(LLVM_ENABLE_PROJECTS STREQUAL "")
           # If `LLVM_ENABLE_PROJECTS` is not being used (implying that we are
           # using the old layout), suggest checking it out.