diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -30,6 +30,21 @@
  "${PROJECT_NAME} requires an out of source build. Please create a separate
  build directory and run 'cmake /path/to/${PROJECT_NAME} [options]' there."
  )
+
+# Show detailed compiler version information when available. This is mainly
+# useful in the CI to determine the exact version of the Clang nightly build
+# used. This information is not available in CMAKE_CXX_COMPILER_VERSION. It may
+# be useful for users using non-release versions of other compilers so don't
+# restrict this to Clang but test whether the compiler supports the version
+# flag.
+execute_process(COMMAND
+  "${CMAKE_CXX_COMPILER}" "--version"
+  OUTPUT_VARIABLE out
+  ERROR_VARIABLE err)
+if(NOT "${out}" STREQUAL "" AND  "${err}" STREQUAL "")
+  message(STATUS "Compiler used:\n${out}")
+endif()
+
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND "${CMAKE_CXX_SIMULATE_ID}" STREQUAL "MSVC")
   message(STATUS "Configuring for clang-cl")
   set(LIBCXX_TARGETING_CLANG_CL ON)