[Lazarus] Runtime package (manual compilation only) forced to re-compile by a design time dependant package?

[patspiper]

On 14/04/13 01:24, Mattias Gaertner wrote:
> On Sat, 13 Apr 2013 22:27:11 +0300
> patspiper <patspiper at gmail.com> wrote:
>
>> [...]
>>>> In what needs building (with the design package selected), the
>>>> runtime package is marked as No build needed. Nevertheless, compiling
>>>> the design time package tries to compile the runtime units.
>>> It turned out that the design time package had a other units path that
>>> included one unit of the runtime package. I know this is a bad
>>> practice, but does it fully explain the observed behaviour?
>> I realise now why they shared the same path, but I am not sure if this
>> is right or wrong. The registration unit of the design time package is
>> in the same folder with the runtime units. Should it be placed in a
>> separate folder?
> Yes.
> Packages should not share sources (.pas files). Otherwise the
> compiler will happily recompile them.
> If you must share sources, you should add -Ur.
1- So sharing Other Units (-Fu) path causes units to recompile. Is there 
any other cause that can trigger an unnecessary recompilation?

2- On the other hand, What Needs Building/Lazarus IDE shows that the IDE 
does not need rebuilding (I changed the IDE build profile):
Target: Lazarus IDE
No build needed.   <------- ?????
File: ../lazarus-svn/

despite that the FCL needs it:
Target: FCL 1.0.1
Clean build needed.  <------- ??????
File: /home/me/Programs/lazarus/lazarus-svn/packager/registration/fcl.lpk
Note: Compiler parameters changed:
   Old=""
   Now=""
   State 
file="/home/me/Programs/lazarus/lazarus-svn/packager/units/i386-linux/FCL.compiled"

3- As shown above, FCL's Old and New compiler parameters are empty 
despite the change in the IDE profile. Should that be the case?

Thanks,
Stephano