Warning about -std=gnu99 in configure

configure

{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gl_cv_header_wchar_h_correct_inline" >&5
$as_echo "$gl_cv_header_wchar_h_correct_inline" >&6; }
  if test $gl_cv_header_wchar_h_correct_inline = no; then
    as_fn_error $? "<wchar.h> cannot be used with this compiler ($CC $CFLAGS $CPPFLAGS).
This is a known interoperability problem of glibc <= 2.5 with gcc >= 4.3 in
C99 mode. You have four options:
  - Add the flag -fgnu89-inline to CC and reconfigure, or
  - Fix your include files, using parts of
    <http://sourceware.org/git/?p=glibc.git;a=commitdiff;h=b037a293a48718af30d706c2e18c929d0e69a621>, or
  - Use a gcc version older than 4.3, or
  - Don't use the flags -std=c99 or -std=gnu99.
Configuration aborted." "$LINENO" 5
  fi