I have several subprojects in my project which are get built every time, even they are not changed and not in main project\'s target dependencies. Is there a way to prevent Xcod
It would seem you have Xcode 4's "Find Implicit Dependencies" enabled. Note that this is enabled by default.
Xcode will then only build the dependencies which are out of date and specified as dependencies (or dependencies of a dependency).
If you find that is not the case, then you may want to investigate what causes the build to retrigger (e.g. generated sources, relinking against dependencies which needed to be rebuilt, etc.).