Help with creating Lib's on Linux

[TinF0il]

I have this code:

library ejemploLibreria;

uses
  SysUtils, Classes, Dialogs;

{$R *.res}

procedure pruebaMensaje (mensaje : string); stdcall;
begin
  ShowMessage (mensaje) ;
end;

exports pruebaMensaje;

begin
end.                   

i have this error when i compile:
project1.lpr(10,15) Error: Identifier not found "ShowMessage"

also if i want to add other units like LCLType or FileUtil i got this error:
project1.lpr(6,12) Fatal: Can't find unit FileUtil used by Project1
project1.lpr(6,12) Fatal: Can't find unit LCLType used by Project1

but this only happens when i want to make Librarys, if i want to make an executable and i add the LCLType and FIleUtil Unit's i dont get that error when compiling and the program run's fine
Im using Linux Mint 8
i would appreciate if you can help me
and sorry my english

[theo]

You need to add LCL as a required package in the project inspector.
This is done automatically for applications but not for libraries.

[TinF0il]

You need to add LCL as a required package in the project inspector.
This is done automatically for applications but not for libraries.

Hey dude! thank's you solved my problem thank you very much!