Just upgraded to Snow Leopard, installed Xcode 3.2, then installed iPhone SDK 3 for SL.
In a project, I now get the following error on build:
I was able to fix this problem by adding the following to my Makefile:
CFLAGS="$(OTHER_CFLAGS) -mmacosx-version-min=10.5"
LDFLAGS="$(OTHER_LDFLAGS) -mmacosx-version-min=10.5"
Ostensibly, this is only required when building outside of Xcode. This problem frustrated me long enough that I figured it would be useful to share my experience here.