Fix local macro packages that depend on SwiftSyntax prebuilts

Local macro packages no longer get forced onto incompatible prebuilt SwiftSyntax modules. Tuist now keeps SwiftPM prebuilt metadata off user-owned local macro targets so they can use SwiftPM’s normal dependency resolution and fall back to building SwiftSyntax from source with the active toolchain. Remote packages still use SwiftSyntax prebuilts, fixing errors like importing SwiftCompilerPlugin from an incompatible .swiftmodule when building local macros.