of virtual targets, not the deep one with the 'str' method. The latter is
very slow
* tools/gcc.jam: Don't declare gcc.link and gcc.link.dll generators, as
they are already inherited from unix.jam. If we declare them, then for
each targets, the whole generation process is run twice. As result,
select-alternative is called for each target, and due to sloweness of
'str' the performance is horrible.
The net result is that running time on one testcase is down from 1580 secs
to less than 10.
[SVN r25512]