calling build_option too early causes a mess

[boegel]

While working on #2110 with @victorusu, we bumped into a hard-to-debug mess by introducing a call to build_option('extended_dry_run') in the symlink function provided by filetools (which got rolled back).

Because symlink is by the handling of the --include-* options, which is done before option parsing fully completes, the BuildOption singleton is being created too early, i.e. before the build options are actually available. In later calls to build_option, the basically empty instance of BuildOption is reused, leading to errors like:

Traceback (most recent call last):
  File "/tmp/200339473/lib/python2.6/site-packages/easybuild_framework-3.1.0-py2.6.egg/test/framework/options.py", line 2090, in test_use_included_module_naming_scheme
    self.eb_main(args, logfile=dummylogfn, do_build=True, raise_error=True, raise_systemexit=True, verbose=True)
  File "/tmp/200339473/lib/python2.6/site-packages/easybuild_framework-3.1.0-py2.6.egg/test/framework/utilities.py", line 293, in eb_main
    raise myerr
EasyBuildError: 'Undefined build option: from_pr'

Potential solutions:

• refactor to avoid that BuildOptions is a singleton;
• avoid taking any actions before completing the option parsing; as it is now, some options like --include-*, --list-* and --avail-* are handled in options.py itself, rather than only parsing the options and letting main.py take care of the handling of the options...