[flang-rt] Fix typo using static instead of shared

Summary:
I copied this from the static usage, replaced the shared on the
dependency but not on the target.

flang-rt/cmake/modules/AddFlangRT.cmake

@@ -143,7 +143,7 @@ function (add_flangrt_library name)
   endif ()
   if (build_shared)
     add_library("${name_shared}" SHARED ${extra_args} ${ARG_ADDITIONAL_HEADERS} ${ARG_UNPARSED_ARGUMENTS})
-    target_link_libraries("${name_static}" PRIVATE flang-rt-libcxx-headers flang-rt-libc-headers flang-rt-libc-shared)
+    target_link_libraries("${name_shared}" PRIVATE flang-rt-libcxx-headers flang-rt-libc-headers flang-rt-libc-shared)
     if (Threads_FOUND) 
       target_link_libraries(${name_shared} PUBLIC Threads::Threads)
     endif ()