[Lazarus] Do not recompile all package dependencies

[Ondrej Pokorny]

If I change compiler settings for a project, all packages have to be 
recompiled as well.

Is there a chance to store the precompiled (object) files of the 
packages in a custom location for a project/build mode?

I tried to set -FU in "Additions and Overrides" to a custom absolute 
path but it doesn't seem to help. Furthermore I get warnings about 
duplicate files:

Note: Duplicate unit "actnlist" in "LCLBase 1.5", 
ppu="P:\software\Lazarus_src\trunk\lcl\units\i386-win32\actnlist.ppu", 
source="P:\software\Lazarus_src\trunk\lcl\actnlist.pas"

etc.

Is there a way to achieve that packages won't be recompiled upon 
project/buildmode change? (= different directories for the precompiled 
files will be used). It takes quite long to recompile the LCL packages.

Ondrej