[flang] Fixed linaro-flang-aarch64-sharedlibs after D145992.

flang/examples/ExternalHelloWorld/CMakeLists.txt

@@ -1,8 +1,9 @@
-set(LLVM_LINK_COMPONENTS
-  FortranRuntime
-  )
-
 # This test is not run by default as it requires input.
 add_llvm_example(external-hello-world
   external-hello.cpp
 )
+
+target_link_libraries(external-hello-world
+  PRIVATE
+  FortranRuntime
+  )