mariadb: fix do_configure failed while multilib is used

Here is the error log from mariadb's configure test
...
 checking for zlib compression library... configure: error: headers or
binaries were not found in /home/jiahongxu/yocto/build-20131009-mysql/
bitbake_build/tmp/sysroots/qemux86-64/usr/{include,lib}
...

When multilib is used, the baselib is assigned with "lib64", here is
the log from 'bitbake mariadb -e'
...
 4738 # $baselib [3 operations]
 4739 #   set conf/bitbake.conf:10
 4740 #     "${BASELIB}"
 4741 #   set conf/bitbake.conf:11
 4742 #     [vardepvalue] "${baselib}"
 4743 #   set /home/jiahongxu/yocto/build-20131009-mysql/layers/oe-core/meta/conf/multilib.conf:2
 4744 #     "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) or 'INVALID'), True) or d.getVar('BASELIB', True)}"
 4745 # computed:
 4746 #   "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE', True) or 'INVALID'), True) or d.getVar('BASELIB', True)}"
 4747 baselib="lib64"
...

In this situation, the zlib locates in 'lib64' rather than 'lib'.
But mariadb's confiure test still searches zlib in 'lib'.

Modify mariadb's confiure to let lib dir configurable rather
than hardcode could fix this issue.

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>