Deduplicate conditioned XCFramework search paths

Fixed a regression where generating large projects with static Swift XCFrameworks behind dynamic XCFrameworks could crash or produce invalid projects because SDK-conditioned FRAMEWORK_SEARCH_PATHS entries were repeated across multiple dependency paths. Settings are now deduplicated when they are merged, so the same conditioned search path is only added once. This also applies the same duplicate cleanup to conditioned OTHER_SWIFT_FLAGS entries.