Explicit Module Builds interop with vfsoverlays

[chiragramani]

We have an existing Xcode project where we make use of vfsoverlays. These overlays have been working well in our previous setups. However, after enabling the Explicit Module Build feature in Xcode 16, our builds start to fail.

It seems like the VFS overlays, although configured correctly and pointing to valid files, are not being honored during the build process. We are unsure if this is a configuration issue or a limitation with the new explicit module build system.

Any insights or suggestions?

[chiragramani]

cc: @artemcm