5.7.6. Rebuild Improvements

Changes have been made to the base, autotools, and cmake classes to clean out generated files when the do_configure task needs to be re-executed.

One of the improvements is to attempt to run "make clean" during the do_configure task if a Makefile exists. Some software packages do not provide a working clean target within their make files. If you have such recipes, you need to set CLEANBROKEN to "1" within the recipe, for example:

     CLEANBROKEN = "1"