Include rpath for the back-deployed Span dylib

Co-authored-by: Owen Voorhees <[email protected]>

Author: DougGregor

Sources/SWBCore/Settings/BuiltinMacros.swift

@@ -602,6 +602,7 @@ public final class BuiltinMacros {
     public static let DISABLE_INFOPLIST_PLATFORM_PROCESSING = BuiltinMacros.declareBooleanMacro("DISABLE_INFOPLIST_PLATFORM_PROCESSING")
     public static let DISABLE_MANUAL_TARGET_ORDER_BUILD_WARNING = BuiltinMacros.declareBooleanMacro("DISABLE_MANUAL_TARGET_ORDER_BUILD_WARNING")
     public static let DISABLE_STALE_FILE_REMOVAL = BuiltinMacros.declareBooleanMacro("DISABLE_STALE_FILE_REMOVAL")
+    public static let DISABLE_SWIFT_SPAN_COMPATIBILITY_RPATH = BuiltinMacros.declareBooleanMacro("DISABLE_SWIFT_SPAN_COMPATIBILITY_RPATH")
     public static let DISABLE_TEST_HOST_PLATFORM_PROCESSING = BuiltinMacros.declareBooleanMacro("DISABLE_TEST_HOST_PLATFORM_PROCESSING")
     public static let DISABLE_XCFRAMEWORK_SIGNATURE_VALIDATION = BuiltinMacros.declareBooleanMacro("DISABLE_XCFRAMEWORK_SIGNATURE_VALIDATION")
     public static let DONT_CREATE_BUILT_PRODUCTS_DIR_SYMLINKS = BuiltinMacros.declareBooleanMacro("DONT_CREATE_BUILT_PRODUCTS_DIR_SYMLINKS")
@@ -1614,6 +1615,7 @@ public final class BuiltinMacros {
         DISABLE_INFOPLIST_PLATFORM_PROCESSING,
         DISABLE_MANUAL_TARGET_ORDER_BUILD_WARNING,
         DISABLE_STALE_FILE_REMOVAL,
+        DISABLE_SWIFT_SPAN_COMPATIBILITY_RPATH,
         DISABLE_TEST_HOST_PLATFORM_PROCESSING,
         DISABLE_XCFRAMEWORK_SIGNATURE_VALIDATION,
         DOCC_ARCHIVE_PATH,

Sources/SWBCore/SpecImplementations/Tools/LinkerTools.swift

@@ -294,11 +294,20 @@ public final class LdLinkerSpec : GenericLinkerSpec, SpecIdentifierType, @unchec
         // And, if the deployment target does not support Swift Concurrency natively, then the rpath needs to be added as well so that the shim library can find the real implementation. Note that we assume `true` in the case where `supportsSwiftInTheOS` is `nil` as we don't have the platform data to make the correct choice; so fallback to existing behavior.
         // The all above discussion is only relevant for platforms that support Swift in the OS.
         let supportsSwiftConcurrencyNatively = cbc.producer.platform?.supportsSwiftConcurrencyNatively(cbc.scope, forceNextMajorVersion: false, considerTargetDeviceOSVersion: false) ?? true
+        let supportsSwiftSpanNatively = cbc.producer.platform?.supportsSwiftSpanNatively(cbc.scope, forceNextMajorVersion: false, considerTargetDeviceOSVersion: false) ?? true
         let shouldEmitRPathForSwiftConcurrency = UserDefaults.allowRuntimeSearchPathAdditionForSwiftConcurrency && !supportsSwiftConcurrencyNatively
-        if (cbc.producer.platform?.supportsSwiftInTheOS(cbc.scope, forceNextMajorVersion: true, considerTargetDeviceOSVersion: false) != true || cbc.producer.toolchains.usesSwiftOpenSourceToolchain || shouldEmitRPathForSwiftConcurrency) && isUsingSwift && cbc.producer.platform?.minimumOSForSwiftInTheOS != nil {
-                // NOTE: For swift.org toolchains, this is fine as `DYLD_LIBRARY_PATH` is used to override these settings.
+        let shouldEmitRPathForSwiftSpan = !cbc.scope.evaluate(BuiltinMacros.DISABLE_SWIFT_SPAN_COMPATIBILITY_RPATH) && !supportsSwiftSpanNatively
+        if (
+            cbc.producer.platform?.supportsSwiftInTheOS(cbc.scope, forceNextMajorVersion: true, considerTargetDeviceOSVersion: false) != true ||
+            cbc.producer.toolchains.usesSwiftOpenSourceToolchain ||
+            shouldEmitRPathForSwiftConcurrency ||
+            shouldEmitRPathForSwiftSpan
+        )
+            && isUsingSwift
+            && cbc.producer.platform?.minimumOSForSwiftInTheOS != nil {
+            // NOTE: For swift.org toolchains, this is fine as `DYLD_LIBRARY_PATH` is used to override these settings.
             let swiftABIVersion =  await (cbc.producer.swiftCompilerSpec.discoveredCommandLineToolSpecInfo(cbc.producer, cbc.scope, delegate) as? DiscoveredSwiftCompilerToolSpecInfo)?.swiftABIVersion
-                runpathSearchPaths.insert( swiftABIVersion.flatMap { "/usr/lib/swift-\($0)" } ?? "/usr/lib/swift", at: 0)
+            runpathSearchPaths.insert( swiftABIVersion.flatMap { "/usr/lib/swift-\($0)" } ?? "/usr/lib/swift", at: 0)
         }
 
         return runpathSearchPaths