Add configure check for -latomic

configure.ac

@@ -54,6 +54,9 @@ case $host in
 esac
 dnl Require C++11 compiler (no GNU extensions)
 AX_CXX_COMPILE_STDCXX([11], [noext], [mandatory], [nodefault])
+dnl Check if -latomic is required for <std::atomic>
+CHECK_ATOMIC
+
 dnl Unless the user specified OBJCXX, force it to be the same as CXX. This ensures
 dnl that we get the same -std flags for both.
 m4_ifdef([AC_PROG_OBJCXX],[