configure: Remove for redirection of built-in functions

configure: Remove for redirection of built-in functions

The check was initially used to define HAVE_BUILTIN_REDIRECTION, which
enables or not libc_hidden_builtin_proto support. It was later removed
with 3ce1f2959437e952b9db4eaeed2407424f11a4d1, making the feature
mandatory. The configure check was kept as a transition knob.

Current minimum gcc/linker always supports this, as well as clang with
some extra care. Also, missing hidden_proto/hidden_def support is
already flagged in the check-localplt test.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>