berkeleydb: workaround m68k/coldfire issue

Fixes:
 http://autobuild.buildroot.net/results/40423aa6c8f6fe66c771cca3e09b21e15525eb5f



Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
[Thomas: rename BERKELEYDB_CONF_OPTS to BERKELEYDB_CONF_ENV.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>