Building on Leopard with Tiger compatibility breaks linked libiconv.2.dylib

[Christiaan Hofman]

We are trying to build our app on Leopard, but it should be compatible  
with 10.4. So we use 10.4 as the deployment target for all our  
targets. However the app won't run on 10.4, it crashes on an  
incompatible version of libiconv.2.dylib. Leopard has version 7.0.0,  
and Tiger has version 5.0.0, according to the crash report.

The particular library is used in a framework included in the app. I  
tried just using the 10.4u SDK for this framework (while still using  
the 10.5 SDK for the main app target, but that shouldn't matter,  
right?). But that did not help.

So what build settings should I use to make this work? I hope I do not  
have to go back to using the 10.4u SDK for my app.

This is the relevant part of a crash report on Tiger (crossing out  
some irrelevant info):

dyld: Library not loaded: /usr/lib/libiconv.2.dylib
  Referenced from: /Applications/MyApp.app/Contents/MacOS/../ 
Frameworks/MyFramework.framework/Versions/A/MyFramework
  Reason: Incompatible library version: MyFramework requires version  
7.0.0
or later, but libiconv.2.dylib provides version 5.0.0
Feb 26 18:30:00 xxxxx crashdump[20018]: MyApp crashed
Feb 26 18:30:00 xxxxx crashdump[20018]: crash report written to: / 
Users/xxxxx/Library/Logs/CrashReporter/MyApp.crash.log

Thanks,
Christiaan