diff --git a/compiler-rt/cmake/Modules/AddCompilerRT.cmake b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
--- a/compiler-rt/cmake/Modules/AddCompilerRT.cmake
+++ b/compiler-rt/cmake/Modules/AddCompilerRT.cmake
@@ -372,13 +372,33 @@
         set_target_properties(${libname} PROPERTIES IMPORT_PREFIX "")
         set_target_properties(${libname} PROPERTIES IMPORT_SUFFIX ".lib")
       endif()
-      if(APPLE)
-        # Ad-hoc sign the dylibs
-        add_custom_command(TARGET ${libname}
-          POST_BUILD
-          COMMAND codesign --sign - $<TARGET_FILE:${libname}>
-          WORKING_DIRECTORY ${COMPILER_RT_OUTPUT_LIBRARY_DIR}
+      if (APPLE AND NOT CMAKE_LINKER MATCHES ".*lld.*")
+        # Ad-hoc sign the dylibs when using Xcode versions older than 12.
+        # Xcode 12 shipped with ld64-609.
+        # FIXME: Remove whole conditional block once everything uses Xcode 12+.
+        set(LD_V_OUTPUT)
+        execute_process(
+          COMMAND sh -c "${CMAKE_LINKER} -v 2>&1 | head -1"
+          RESULT_VARIABLE HAD_ERROR
+          OUTPUT_VARIABLE LD_V_OUTPUT
         )
+        if (HAD_ERROR)
+          message(FATAL_ERROR "${CMAKE_LINKER} failed with status ${HAD_ERROR}")
+        endif()
+        set(NEED_EXPLICIT_ADHOC_CODESIGN 1)
+        if ("${LD_V_OUTPUT}" MATCHES ".*ld64-([0-9.]+).*")
+          string(REGEX REPLACE ".*ld64-([0-9.]+).*" "\\1" HOST_LINK_VERSION ${LD_V_OUTPUT})
+          if (HOST_LINK_VERSION VERSION_GREATER_EQUAL 609)
+            set(NEED_EXPLICIT_ADHOC_CODESIGN 0)
+          endif()
+        endif()
+        if (NEED_EXPLICIT_ADHOC_CODESIGN)
+          add_custom_command(TARGET ${libname}
+            POST_BUILD
+            COMMAND codesign --sign - $<TARGET_FILE:${libname}>
+            WORKING_DIRECTORY ${COMPILER_RT_OUTPUT_LIBRARY_DIR}
+          )
+        endif()
       endif()
     endif()