Fix the version extraction regex for clang.

Tests/Module/CheckCXXCompilerFlag/CMakeLists.txt

@@ -25,7 +25,7 @@ endif()
 
 if(CMAKE_CXX_COMPILER_ID MATCHES Clang)
   exec_program(${CMAKE_CXX_COMPILER} ARGS --version OUTPUT_VARIABLE     _clang_version_info)
-  string (REGEX MATCH "version [345]\\.[0-9]" _clang_version "${_clang_version_info}")
+  string (REGEX REPLACE ".*version ([0-9]\\.[0-9]).*" "\\1" _clang_version "${_clang_version_info}")
 endif()
 
 message("Platform:\n  WIN32: ${WIN32}\n  UNIX: ${UNIX}\n  APPLE: ${APPLE}\n  MINGW: ${MINGW}\n  CYGWIN: ${CYGWIN}\n"