Removing kind-of-obvious three dots.
Here is the mindless output of the original command.
./configure BDB_LIBS="-L${BDB_PREFIX}/lib -ldb_cxx-4.8" BDB_CFLAGS="-I${BDB_PREFIX}/include" ...
configure: WARNING: you should use --build, --host, --target
checking build system type... Invalid configuration `...': machine `...' not recognized
configure: error: /bin/sh build-aux/config.sub ... failed```