Builder compatibility, bug?

[Charles Crain]

I am using the LinkedModule command as suggested in the Cons FAQ to "squish"
together object files generated by subordinate Conscripts, so that a
top-level Conscript can eventually find and link them.  So for instance, my
top level Conscript might look like:

Export qw( env );

Build( "foo/Conscript",
        "bar/Conscript" );

Library $env "foo.cpp",
        "bar.cpp",
        "objs.o";

...then for instance foo/Conscript (or bar/Conscript) might look like:

Import qw( env );

LinkedModule $env "../objs.o",
        "baz.cpp",
        "blah.cpp";

As the FAQ suggests, this approach is cool because it allows the top-level
Conscript to be ignorant of the exact set of object files produced by its
subordinates.  However, my problem is this: if I try to modify the
construction environment in one of the subordinate Conscripts, like:

Import qw( env );

$env = $env->clone(CPPPATH => [ @{$env->{CPPPATH}},
"#some/include/directory" ]);

LinkedModule $env "../objs.o",
        "baz.cpp",
        "blah.cpp";

Then I get the following error:

cons: error in file "Conscript":
        objs.o
        built (at least) two different ways:
                Conscript, line 13:  cons::Library
                foo/Conscript, line 5:  cons::LinkedModule

This error goes away if I do not try to modify the construction environment.
What gives?  As I understand the error, it is only supposed to pop up if I
am trying to build objs.o with two incompatible builders, but I am only
building it with LinkedModule.  Library is not building objs.o; it is using
it.  Is this a bug?

Thanks,
Charles