Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -390,8 +390,12 @@
     set(LIBCXXABI_LIBUNWIND_SOURCES "")
   endif()
 
-  include_directories("${LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL}")
-  include_directories("${LIBCXXABI_LIBUNWIND_SOURCES}")
+  if (NOT LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL STREQUAL "LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL-NOTFOUND")
+    include_directories("${LIBCXXABI_LIBUNWIND_INCLUDES_INTERNAL}")
+  endif()
+  if (NOT LIBCXXABI_LIBUNWIND_SOURCES STREQUAL "")
+    include_directories("${LIBCXXABI_LIBUNWIND_SOURCES}")
+  endif()
 endif()
 
 # Add source code. This also contains all of the logic for deciding linker flags