Sequel Pro has no external dependencies or Interface Builder plugins, so building is fairly straightforward.
However, we are currently targeting 10.5 as a minimum version (not for much longer!), so the Base SDK is set to 10.5 to correctly report warnings. Xcode 4 does not ship with the 10.5 SDK; to install them:
1) Find a copy of Xcode 3. If you do not have this installed, it is still available
from http://adcdownload.apple.com/Developer_Tools/xcode_3.2.6_and_ios_sdk_4.3__final/xcode_3.2.6_and_ios_sdk_4.3.dmg .
2) Install or extract the 10.5 SDK (and the 10.6 SDK for use soon...). These would normally
have been installed to /Developer/SDKs/MacOSX10.5.sdk and MacOSX10.6.sdk .
3) Copy, or symlink them, into
After performing these steps 10.5- and 10.6-base SDKs should compile correctly (although without PPC support). You may need to quit and reopen Xcode to get it to recognise the new SDKs.
For assistance please jump onto IRC and join #sequel-pro on irc.freenode.net and any of the developers will be more than happy to help you out.