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.