[Libreoffice] Suggestion: Let's change "solver/<mysterious number>/<cryptic platform identification>" to just "staging"

I suggest that we in master get rid of the two subdirectory levels under "solver" (or, as those who 
have worked in Hamburg tend to say, "*the* solver") and rename the "solver" directory to something 
meaningful.

Surely nobody in LibreOffice is using the same build tree for several "master workspaces" (isn't 
that OOo concept is what the <mysterious number> corresponds to?) and architectures, thus there is 
no need to have these two directory levels under "solver".

I am open to suggestions what would be a better name. My own suggestion is "staging". Or perhaps 
even the stuff in the "workdir" of the new gnu make build system could be moved one level up, and 
"solver" renamed to "workdir"?

I don't like renaming "solver" to "build", as that word is already too overloaded: 1) the "build" 
repo and its use to build LibreOffice for distros with patches, 2) the subdirectory called "build" 
that is created in a clone of the "build" repo during such a build, and 3) the "build" shell alias 
for the "build.pl" script.

--tml