xrootd: allow to specify lib/lib64 libdir through 'libdir_name' kwarg
hwaf-base: import os.environ into ctx.env
hwaf-base: add FC and LINK_FC to runtime env. vars
hwaf-base: fixed last remnant of migration to with_xyz_incdir/libdir
hwaf-base: support for multiple tags in hwaf_select_value
hwaf-base: automatically load extra modules when hwaf_export
hwaf-base: more debug infos