Script configuration

The `config' file consists theese variables in a sample :

• WORK_ROOT=/usr/work - a prefix for logs and all the rest of directory structure
• INSTALL_PREFIX=/usr - where to install this stuff. DO NOT use /usr/local here, be warned! It causes an old and outdated versions to persist in a system and cause a crushes and build failures. We do not use any hyper-tweaks for the build process, so the standart libraries can be safely used from this script's results.
• ARCH_DIR=$WORK_ROOT/archive - a folder for archives downloaded from Internet. It's useful to have it on an external or network drive if you're building on Raspberry Pi or similar embedded device. Default settings just resides it under WORK_ROOT path.
• REPO_DIR=$WORK_ROOT/repo - SCM cloned repo directory. Same as above - see ARCH_DIR
• JOBS=8 - concurrent build jobs to launch. It's heavily depends on your system configuration. Use a number of your PHYSICAL cores(in case of Intel CPU there are a HyperThreading ones also) and keep in mind your memory size. If you're using Rasberry Pi - put 1 here, if you're building on it directly
• NO_SCM=0 - If set to 1, the script will skip SCM updates. Quite useful for debugging your own modules in the whole chain without bothering GitHub or something with a frequent queries.
• BUILD_PRESERVE=0 - If set to 1, $WORK_ROOT/build will not be wiped out before extractions
• FULL_EXTRACTION_FIRST=1 - If set to 0, modules will not be extracted ALL before the building process

You can add your additions' configuration variables after them - they will be populated at start before parsing any of the definitions.