Xcode Cannot find a Static Library During Linking even though it is a referenced product

I have two pre-existing Xcode workspaces. One, Parent.xcworkspace is an iOS application. The other SomeChild.xcworkspace is a C++ static library. The SomeChild workspace is in a git submodule of the Parent workspace.

I want to take one project from the SomeChild workspace and add it to the Parent.xcworkspace so that the code is built and statically linked when dependent projects in the Parent workspace are built.

It almost works, but at link time when building the Parent workspace iOS application the linker emits

clang: error: no such file or directory: '/Users/me/Library/Developer/Xcode/DerivedData/Parent-hagqyrdsdfsdfsdfphgbsolz/Build/Products/Debug-iphonesimulator/libSomeChild.a'

It's true, libSomeChild.a does not exist in the directory ending with -iphonesimulator/

libSomeChild does exist in

/Users/me/Library/Developer/Xcode/DerivedData/Parent-hagqyrdsdfsdfsdfphgbsolz/Build/Products/Debug/

So, in summary: The lib is being output to a path that is almost the same as in the error, except without the -iphonesimulator suffix.

How do I fix this build?

Edit:

This question is very similar but doesn't really have an answer Xcode 6.1 static library .a for iOS not generated