R14A can't cross-compile due to ssl certs examples

[Steve Vinoski]

Cross-building the current dev branch of R14A fails due to the
lib/ssl/examples/certs directory. It tries to run the openssl command
based on the target architecture rather than the build architecture.

In erts/configure.in at line 3608, we have this:

                    if test "$cross_compiling" = "yes"; then
                        dnl Cannot test it; hope it is working...
                        OPENSSL_CMD="$SSL_BINDIR/openssl"

which can't work if the openssl executable was built for the target
architecture and so can't execute on the build architecture.

IMO it would be nice if one could just override OPENSSL_CMD in the
xcomp file or even with an environment variable.

--steve