Regtest profiling differences

[Dan Eble]

I've noticed a subjective increase in profiling differences in regtests since 
updating to the latest master this morning 
(bc8a3fa7e4f12bf5ac1eb0293bfab658d52c4ae8), even from one run to another on 
unchanged code.

There are also log differences that might be correlated, with some test cases 
having

-
-Writing timing to ./lily-run-total.profile...
-Success: compilation successfully completed

and others having

+
+Writing timing to ./lily-run-total.profile...
+Success: compilation successfully completed

I've only run regtests a couple of times so far, so I'm not sure how repeatable 
this is.  Were there recent changes that might contribute to this?  Nothing 
stands out to me in the headlines.

Thanks,
— 
Dan