Added new BC test

Updated throughout to use the "temp_build_files" dir on the build drive rather than the "generated" directory in the fbf source tree.

Moved the generation of the release metadata entry for the MD5 zip outside of the parallel section, so it can't co-incide with the zipping of the binaries. Ensured that any errors generated when merging log files are not just hidden by putting them in the output file (which will render it not well-formed XML).

Replaced <available> check with an <uptodate> check, to greatly help people working on the FBF who want the file automatically regenerated according to the changes they have made.

Restored call to summarise final BRAG status for regular platform builds.

Major packaging change to work around parallel calls - stopped zipping targets from having direct dependency on 'sf-preprocess-package-config', and instead have 'sf-zip-content' call 'sf-preprocess-package-config' if needed. Changed 'sf-prep' to call a target that wipes out the 'generated' directory. It's not perfect but it gets us going again.

Moved invocation of sf-brag-to-diamonds, so it's right at the end of the postbuild (apart from publishing zipped logs). This avoids the possibility of a build abort when parallel threaqds are trying to a) convert a log file into a brag file, and b) merge all brag files ready to determine the brag status. It also makes more sense - don't calculate or send the BRAGG status until the build is on the cusp of completion.