Support for using host workdir inside container; change default container workdir to /container/bits/sw

[smuzaffar]

This PR proposes to change the default build location when docker is used. Currently build with docker uses /sw and the new relocate all change will try to relocate all file with /sw in them. As /sw is very generic so there is a good chance that relocation script can do unwanted changes. This PR proposes to change default workdir inside container to /container/bits/sw e.g. we mount <host>/workdir to /container/bits/sw.

A new command-line option --container-use-workdir is also added which will mount <host>/workdir to <host>/workdir inside container. This allows to have local packages build with correct path and one should be able to use them directly (on correct OS/ARCH host) or start a container without explicitly mounting <host>/workdir to some magic /container/bits/sw path.

[smuzaffar]

by the way @ktf , was there any specific reason to build under /sw in docker? Currently the local build area is only usable if one starts docker and explicitly mount $WORK_DIR:/sw. Why not mount $WORK_DIR as it is under docker -v $WORK_DIR:$WORK_DIR?

[ktf]

I think it was to keep the path short, because at some point our $WORK_DIR was a very long path to a temporary directory.

[ktf]

Please, do not use /docker since I am about to introduce some "non docker" container backend.

[smuzaffar]

Please, do not use /docker since I am about to introduce some "non docker" container backend.

sure
I would like to use -v $WORK_DIR:$WORK_DIR so that the local build area is usable but if you want to have a fixed short path inside docker then may be we can add a command-line option --docker-use-workdir which uses -v $WORK_DIR:$WORK_DIR otherwise use -v $WORK_DIR:/container/bits/build ?

[ktf]

Sounds good to me.

[smuzaffar]

I have updated the PR and its description. Now default workdir inside container is /container/bits/sw . also added --container-use-workdir to use host's workdirectory inside container