Fix macOS linker option, again

Author: redsun82

patches/swift/04-allow-plugging-in-observer.patch

@@ -58,7 +58,7 @@ index 184e6196918..ef5c3eafe69 100644
    // progress.
  };
 diff --git a/lib/AST/CMakeLists.txt b/lib/AST/CMakeLists.txt
-index ec3fa2c853b..c4afddc4940 100644
+index ec3fa2c853b..7ea1a1763b9 100644
 --- a/lib/AST/CMakeLists.txt
 +++ b/lib/AST/CMakeLists.txt
 @@ -58,7 +58,6 @@ add_swift_host_library(swiftAST STATIC
@@ -78,7 +78,7 @@ index ec3fa2c853b..c4afddc4940 100644
 +        )
 +
 +if(${SWIFT_HOST_VARIANT_SDK} IN_LIST SWIFT_DARWIN_PLATFORMS)
-+  target_link_options(swiftIdentifier PRIVATE "-undefined dynamic_lookup")
++  target_link_options(swiftIdentifier PRIVATE "LINKER:-undefined,dynamic_lookup")
 +endif()
 +
  if(SWIFT_FORCE_OPTIMIZED_TYPECHECKER)