introduce gb_Package_PRESTAGEDIR

this introduces a "prestage dir" -- if a file can be found in that
directory, it will be copied over instead of build. Usecases for this
include:

- split builds:
e.g. a part of the LibreOffice gets build by a core package and
"writer" or "calc" package then only builds the additional missing
pieces (while copying existing files from the earlier package build)
please not this does not intend to produce separately installable
instances, only to generate the build in multiple steps, to:
- reduce filesystem usage of one build
- paralellisation: e.g. "writer" and "calc" could build at the same
time on two builders
- restart capability: e.g. if a build breaks in "writer", no need to
rebuild everything (relevant for slow and somewhat more flaky
platforms like arm)
- staged single build:
on a filesystem restrained builder, keeping all the objects around for
the build can be a burden. With this, such builders can do a partial
build (lets say: "make svx"), put the instdir aside, make clean and
continue -- but without needing to keep space for the object files of
the build up to svx.

It need gb_RUNNABLE_INSTDIR -- we are going there anyway, no need to
support other scenarios.

This needs more dependency breaking for most scenarios but a:

export gb_RUNNABLE_INSTDIR=T
make
cp -a instdir instdir_prestage
make clean
make sw.all
make sw.clean
export gb_Package_PRESTAGEDIR=`readlink -f instdir_prestage/unxlngx6.pro`
cd sw && make build # this does no compiles, it just copies

Change-Id: I22d4208b2fad0d8fc59426ba4c8c52122876f646
Reviewed-on: https://gerrit.libreoffice.org/5591
Reviewed-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>
Tested-by: Björn Michaelsen <bjoern.michaelsen@canonical.com>

0 files changed, 0 insertions, 0 deletions