Apply one more portability patch from Dan McMahill

Apply one more portability patch from Dan McMahill

patch-ae -- $$(command) is ok with bash and ksh but is not portable to
            all /bin/sh implementations.  Also instead of hard coding
            "apxs2" use the APXS2 variable which was set during the
             configure process. This is especially helpful when the
             binary is installed as apxs instead of apxs2.

             Finally, remove the DEF_LDLIBS from the apxs2 compilation/link
             line.  As near as I can tell this only removed -lopensrf which
             is ok because we already had libopensrf.so explicitly listed.
             Including -lopensrf didn't work correctly since libopensrf
             had been built but not yet installed.

Developer's Certificate of Origin 1.1

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    have the right to submit it under the open source license
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(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
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(c) The contribution was provided directly to me by some other
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Signed-off-by: Dan McMahill <dmcmahill@NetBSD.org>
git-svn-id: svn://svn.open-ils.org/OpenSRF/branches/rel_1_2@1908 9efc2488-bf62-4759-914b-345cdb29e865