--- hdf-4.2.15/configure.ac.orig	2020-11-11 21:29:50.130673804 +0100
+++ hdf-4.2.15/configure.ac	2020-11-11 22:31:12.350725506 +0100
@@ -701,6 +701,7 @@
       if test -z "$HAVE_OLDRPC" ; then
         LIBS="$LIBS -ltirpc"
         CPPFLAGS="$SYSCPPFLAGS -I/usr/include/tirpc"
+	unset ac_cv_header_rpc_rpc_h
         AC_CHECK_HEADER([rpc/rpc.h],[:], [unset HAVE_TIRPC])
         if test -z "$HAVE_TIRPC" ; then
           CPPFLAGS="$SYSCPPFLAGS"