Install method fails on absolute path?

[Timothee Besset]

I'm trying to do something like that:
Install $env $INSTALL_DIR, "radiant";

where INSTALL_DIR is a variable I imported with an absolute path. It
looks like the installation is not performed. However if I use a
relative path to the toplevel Construct file it seems to work:
Install $env '#install', "radiant";

Only info I found which could be related to my problem is:
http://www.baldmt.com/cons-faq/current.html#SS_7_5

right now I'm using a symlink in #install to my absolute path and it
seems to work (yuck)

(I'm using cons 2.2.0)

TTimo