$NetBSD$

test ... == ... is not portable.

--- configure.orig	2018-10-09 07:29:07.000000000 +0000
+++ configure
@@ -5691,7 +5691,7 @@ if test "x$ac_cv_prog_cc_c99" != xno; th
 fi
 
 
-if test "$ac_cv_prog_cc_c99" == "no"; then
+if test "$ac_cv_prog_cc_c99" = "no"; then
     as_fn_error $? "Valgrind relies on a C compiler supporting C99" "$LINENO" 5
 fi
 
