[runtimes] Print the testing configuration in use in libunwind and libc++abi

We do it for libc++, and it's rather useful for debugging e.g. CI.

GitOrigin-RevId: c631e33f316d891b39c1e01217a7422fdc29ced1
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8d583df..e7e29dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -198,6 +198,7 @@
 if (NOT IS_ABSOLUTE "${LIBCXXABI_TEST_CONFIG}")
   set(LIBCXXABI_TEST_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/test/configs/${LIBCXXABI_TEST_CONFIG}")
 endif()
+message(STATUS "Using libc++abi testing configuration: ${LIBCXXABI_TEST_CONFIG}")
 set(LIBCXXABI_TEST_PARAMS "" CACHE STRING
     "A list of parameters to run the Lit test suite with.")