[libc++] Rename LIBCXX_ENABLE_DEBUG_MODE to LIBCXX_ENABLE_DEBUG_MODE_SUPPORT
To make it clearer this is about whether the library supports the debug
mode at all, not whether the debug mode is enabled. Per comment by Nico
Weber on IRC.
diff --git a/libcxx/cmake/caches/Generic-nodebug.cmake b/libcxx/cmake/caches/Generic-nodebug.cmake
index b301b2e..a62760fa 100644
--- a/libcxx/cmake/caches/Generic-nodebug.cmake
+++ b/libcxx/cmake/caches/Generic-nodebug.cmake
@@ -1 +1 @@
-set(LIBCXX_ENABLE_DEBUG_MODE OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_DEBUG_MODE_SUPPORT OFF CACHE BOOL "")