Yes, swift packages can be built as mergeable. Though it currently takes more build options than just using an Xcode setting. In the package manifest, you would need to pass -Wl,-make_mergeable in unsafeFlags in the linkerSettings. You also need to ensure the library's type is explicitly set to .dynamic too, otherwise, the build system could default differently.
This also may require setting adding linker options for clients merging the package. For more information, review https://developer.apple.com/documentation/Xcode/configuring-your-project-to-use-mergeable-libraries#Manually-configure-merging
c_ishida
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