[patch] jdbc build fix when ./configure is run in separate dir

tim@keow.org wrote:

When ./configure is run outside the source directory
(to keep the build files separate from the source files),
make fails for the jdbc target because ant is not informed
of the configure/build directory location.

This patch fixes this, but could you please review it
for portability, etc. For example, I am not sure that
`pwd` is the best way to find the configure/build dir.

JDBC is moving to gborg for 7.5 so this patch isn't required.

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