configure: remove useless NPTL probe

Using a linuxthreads system with a recent QEMU will have bigger problems
than just not having NPTL.  Remove the unnecessary check.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -1994,25 +1994,6 @@ if ! has "$pkg_config_exe"; then
   error_exit "pkg-config binary '$pkg_config_exe' not found"
 fi
 
-##########################################
-# NPTL probe
-
-if test "$linux_user" = "yes"; then
-  cat > $TMPC <<EOF
-#include <sched.h>
-#include <linux/futex.h>
-int main(void) {
-#if !defined(CLONE_SETTLS) || !defined(FUTEX_WAIT)
-#error bork
-#endif
-  return 0;
-}
-EOF
-  if ! compile_object ; then
-    feature_not_found "nptl" "Install glibc and linux kernel headers."
-  fi
-fi
-
 ##########################################
 # xen probe