milter-greylist fails to cross build from source, because it uses
AC_RUN_IFELSE in multiple occasions. In this bug report, I'm considering
only the first two of them. There, we want to check whether linking
-lcurl requires -lcrypto. In this case, running the program does not
yield any added value. We are using no symbols from either library and
if running fails, linking should fail already. Thus, I am proposing to
change AC_RUN_IFELSE to AC_LINK_IFELSE here. I'm attaching a patch for
your convenience.

Note that this patch does not make milter-greylist cross buildable.
That's ok. Please close this bug anyway when doing something about the
-lcurl test.

Helmut