Sorry for posting another solution so late. I had found this solution long time back when i was trying to find a solution that would save me from the manual work of creating a universal library using lipo command every time i had to build the universal library.
So, here is the another approach, for those using aggregate approach to build the universal library
just make one small change as mentioned below in your aggregate script for simulator to build the universal library -
xcodebuild -target ProductName -configuration ${CONFIGURATION} -sdk iphonesimulator ARCHS="i386 x86_64" BUILD_DIR="${BUILD_DIR}" BUILD_ROOT="${BUILD_ROOT}" SYMROOT="${SYMROOT}"
Please observe the inclusion of multiple architectures instead of using single architecture approach -
xcodebuild -target ProductName -configuration ${CONFIGURATION} -sdk iphonesimulator -arch i386 BUILD_DIR="${BUILD_DIR}" BUILD_ROOT="${BUILD_ROOT}" SYMROOT="${SYMROOT}"
Just ARCHS="i386 x86_64" will do the magic for you.
You can confirm this by using the following lipo command
lipo -info newLibraryName.a
Hope this saves time for many others like me!!!