[sldev] SCons fully recompiles every time? (Ubuntu 7.04)

[ac251404 at ohio.edu]

I have tried this on my both my laptop and desktop both running Ubuntu Feisty
7.04. I followed the wiki instructions for getting the source and compiling the
viewer with this command - 'scons DISTCC=no BTARGET=client BUILD=release
MOZLIB=no'. Everything compiles and works fine. Took about 130 minutes on my
laptop (1.5ghz PM, 512mb) and about 40 minutes on my desktop (2Ghz intel dual
core, 2GB ram). I did not attempt to use the -j option as I did not find about
it later. So the viewer runs fine and had no compilation issues, but if I issue
the build command again (making no changes to the source, not even opening a
file) it still takes the full amount of time to compile (130/40 mins). Is there
some flag I am missing for SCons? Everyone else seems to be able to rebuild in a
few minutes, so why is mine building from scratch? 

More info - I am using the linux pre-compiled libs as per the instructions on
the wiki and have also included the fmod library. Also have installed packages
for gcc 3.4, flex and bison.

If anyone has any ideas I'd really appreciate it. We are using the viewer for my
software design class and having an hour compile time for each change I make is
really hurting my productivity.

Thanks,
-Alex c.