run rtds test up to 10x

test/runtests.jl

@@ -463,20 +463,21 @@ end
     end
     Ts = subtypes(Any)[1:20]   # we don't need all of them
     mappushes!(spell_spec, [], Ts)
-    while Profile.len_data() == 0
+    rtds = []
+    for _ in 1:10 # try to get a runtime dispatch on unfortunately flaky profiling
         @profile for i = 1:10000
             mappushes!(spell_spec, [], Ts)
         end
-    end
-    _, sfdict = Profile.retrieve()
-    rtds = []
-    for sfs in values(sfdict)
-        for sf in sfs
-            if (FlameGraphs.status(sf) & FlameGraphs.runtime_dispatch) != 0
-                push!(rtds, sfs)
-                break
+        _, sfdict = Profile.retrieve()
+        for sfs in values(sfdict)
+            for sf in sfs
+                if (FlameGraphs.status(sf) & FlameGraphs.runtime_dispatch) != 0
+                    push!(rtds, sfs)
+                    break
+                end
             end
         end
+        isempty(rtds) || break
     end
     @test !isempty(rtds)
 end