Add -undefined dynamic_load to swiftIdentifier

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..9bf73c9b2fc 100644
+index ec3fa2c853b..f9a23399738 100644
 --- a/lib/AST/CMakeLists.txt
 +++ b/lib/AST/CMakeLists.txt
 @@ -58,7 +58,6 @@ add_swift_host_library(swiftAST STATIC
@@ -69,18 +69,22 @@ index ec3fa2c853b..9bf73c9b2fc 100644
    ImportCache.cpp
    IndexSubset.cpp
    InlinableText.cpp
-@@ -122,6 +121,10 @@ add_swift_host_library(swiftAST STATIC
+@@ -122,6 +121,14 @@ add_swift_host_library(swiftAST STATIC
    ${SWIFTAST_LLVM_LINK_COMPONENTS}
    )
 
 +add_swift_host_library(swiftIdentifier SHARED
 +        Identifier.cpp
 +        )
++
++if(${SWIFT_HOST_VARIANT_SDK} IN_LIST SWIFT_DARWIN_PLATFORMS)
++  target_link_options(swiftIdentifier "-undefined dynamic_load")
++endif()
 +
  if(SWIFT_FORCE_OPTIMIZED_TYPECHECKER)
    if(CMAKE_CXX_COMPILER_ID STREQUAL MSVC OR CMAKE_CXX_SIMULATE_ID STREQUAL MSVC)
      target_compile_options(swiftAST PRIVATE /O2 /Ob2)
-@@ -152,7 +155,7 @@ if(NOT SWIFT_BUILD_ONLY_SYNTAXPARSERLIB)
+@@ -152,7 +159,7 @@ if(NOT SWIFT_BUILD_ONLY_SYNTAXPARSERLIB)
  endif()
 
  target_link_libraries(swiftAST