build: remove already tested headers from AC_CHECK_HEADERS

These headers are already included in a default set which are checked
early during configure.

We already use at least sys/types.h and unistd.h unconditionally in
configure.

Author: fanquake

configure.ac

@@ -1006,7 +1006,7 @@ if test "$TARGET_OS" = "darwin"; then
   AX_CHECK_LINK_FLAG([-Wl,-bind_at_load], [HARDENED_LDFLAGS="$HARDENED_LDFLAGS -Wl,-bind_at_load"], [], [$LDFLAG_WERROR])
 fi
 
-AC_CHECK_HEADERS([endian.h sys/endian.h byteswap.h unistd.h sys/types.h sys/stat.h sys/select.h sys/prctl.h sys/sysctl.h vm/vm_param.h sys/vmmeter.h sys/resources.h])
+AC_CHECK_HEADERS([endian.h sys/endian.h byteswap.h sys/select.h sys/prctl.h sys/sysctl.h vm/vm_param.h sys/vmmeter.h sys/resources.h])
 
 AC_CHECK_DECLS([getifaddrs, freeifaddrs],[CHECK_SOCKET],,
     [#include <sys/types.h>