- flag for an option to set if changing it will trigger a new 'make depend'
- same for 'make clean'
- Specify files to be removed on clean.
- PROG_*_DETECT, LIB_*_DETECT
- static compilation
- error message for './build.sh uqm asdasddsa'
- option to (re)generate files from config.state
  (useful for automatic building)
- generating tags files

some docs
  - sc2_LDFLAGS etc are only relevant in the top dir
  - some variables are 'inherited' from parent dir
  - files are sourced (.)
  - make clean
  - make distclean
    - .depend files
  - description of files

