Index: lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt
===================================================================
--- lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt
+++ lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt
@@ -1,3 +1,11 @@
+# Ignore undef of __register_frame / __deregister_frame
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  # TODO: see if -rtlib flag exists in CMAKE_SHARED_LINKER_FLAGS, then get
+  #       output of -print-libgcc-file-name, do removal only when output is
+  #       compiler-rt.
+  string(REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+endif()
+
 add_llvm_library(LLVMRuntimeDyld
   JITSymbol.cpp
   RTDyldMemoryManager.cpp
Index: unittests/Support/DynamicLibrary/CMakeLists.txt
===================================================================
--- unittests/Support/DynamicLibrary/CMakeLists.txt
+++ unittests/Support/DynamicLibrary/CMakeLists.txt
@@ -19,6 +19,9 @@
     PipSqueak.cpp
     )
   set_target_properties(${NAME} PROPERTIES FOLDER "Tests")
+  if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    target_link_libraries(${NAME} PRIVATE gcc_s)
+  endif()
 
   set_output_directory(${NAME}
     BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}