diff --git a/llvm/cmake/modules/AddLLVM.cmake b/llvm/cmake/modules/AddLLVM.cmake
--- a/llvm/cmake/modules/AddLLVM.cmake
+++ b/llvm/cmake/modules/AddLLVM.cmake
@@ -240,8 +240,14 @@
         set_property(TARGET ${target_name} APPEND_STRING PROPERTY
                      LINK_FLAGS " -Wl,-dead_strip")
       elseif(${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
-        set_property(TARGET ${target_name} APPEND_STRING PROPERTY
-                     LINK_FLAGS " -Wl,-z -Wl,discard-unused=sections")
+        # Support for ld -z discard-unused=sections was only added in
+        # Solaris 11.4.
+        include(CheckLinkerFlag)
+        check_linker_flag("-Wl,-z,discard-unused=sections" LINKER_SUPPORTS_Z_DISCARD_UNUSED)
+        if (LINKER_SUPPORTS_Z_DISCARD_UNUSED)
+          set_property(TARGET ${target_name} APPEND_STRING PROPERTY
+                       LINK_FLAGS " -Wl,-z,discard-unused=sections")
+        endif()
       elseif(NOT WIN32 AND NOT LLVM_LINKER_IS_GOLD AND
              NOT ${CMAKE_SYSTEM_NAME} MATCHES "OpenBSD|AIX")
         # Object files are compiled with -ffunction-data-sections.