Can't build proton-c - undefined symbols ERR_get_error etc

As initially discussed on mail thread..

We are having problems building proton-c on our dev boxes (Red Hat
Enterprise Linux Server release 5.3 (Tikanga)). I've done a git
bisect and discovered that it was Andrew's commit last Wednesday (rev
1417553) that has introduced/exposed the issue. Before that point, we
could build without this issue.

It appears to be a link issue with openssl. The following version of
openssl is installed:

$rpm -q openssl
openssl-0.9.8e-7.el5.x86_64
openssl-0.9.8e-7.el5.i686

Make is failing with the following (complete cmake/make output attached below)

Linking C shared library libqpid-proton.so
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `_log_ssl_error':
openssl.c.text+0x2de): undefined reference to `ERR_get_error'
openssl.c.text+0x2ff): undefined reference to `ERR_error_string_n'
openssl.c.text+0x31c): undefined reference to `ERR_get_error'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `ssl_failed':
openssl.c.text+0x43f): undefined reference to `ERR_get_error'
openssl.c.text+0x45f): undefined reference to `ERR_error_string_n'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `get_dh2048':
openssl.c.text+0x4ac): undefined reference to `DH_new'
openssl.c.text+0x4d7): undefined reference to `BN_bin2bn'
openssl.c.text+0x4f8): undefined reference to `BN_bin2bn'
openssl.c.text+0x526): undefined reference to `DH_free'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `pn_ssl_domain':
openssl.c.text+0x71e): undefined reference to
`OPENSSL_add_all_algorithms_noconf'
openssl.c.text+0x8fd): undefined reference to `DH_free'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `pn_ssl':
openssl.c.text+0x1979): undefined reference to
`OPENSSL_add_all_algorithms_noconf'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `process_input_ssl':
openssl.c.text+0x1cd2): undefined reference to `BIO_write'
openssl.c.text+0x1d62): undefined reference to `BIO_ctrl'
openssl.c.text+0x1dcf): undefined reference to `BIO_read'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function
`process_output_ssl':
openssl.c.text+0x2268): undefined reference to `BIO_write'
openssl.c.text+0x240e): undefined reference to `BIO_read'
openssl.c.text+0x24b7): undefined reference to `BIO_ctrl'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function `init_ssl_socket':
openssl.c.text+0x26a3): undefined reference to `BIO_new'
openssl.c.text+0x26fa): undefined reference to `BIO_ctrl'
openssl.c.text+0x2719): undefined reference to `BIO_new_bio_pair'
openssl.c.text+0x278f): undefined reference to `BIO_ctrl'
openssl.c.text+0x27cf): undefined reference to `BIO_ctrl'
CMakeFiles/qpid-proton.dir/src/ssl/openssl.c.o: In function
`release_ssl_socket':
openssl.c.text+0x2816): undefined reference to `BIO_free'
openssl.c.text+0x284c): undefined reference to `BIO_free'
openssl.c.text+0x2866): undefined reference to `BIO_free'

I am not able to determine the underlying cause (my C skills are ten
years rusty), would someone be able to take a look and advise?