DCE bake build causes waf to prefer libraries in $DCE_HOME/build/lib

[tomhenderson]

When using bake, DCE quagga libraries are placed in $DCE_HOME/build/lib as part of the install process. Later, if one recurses into the source/ns-3-dce directory and edits a file such as myscripts/ns-3-dce-quagga/test/dce-quagga-test.cc, and does not install the new version, the build output suggests that the library is rebuilt locally, but the shared test library linked is the one that was installed earlier in ../../build/lib.

This is in contrast to ns-3 behavior where the locally built libraries are always preferred to bake installed ones.

This may be automatically fixed when this project is cut over (eventually) to CMake.