Replace Opt_SccProfilingOn flag with sccProfilingEnabled helper function
SCC profiling was enabled in a convoluted way: if WayProf was enabled,
Opt_SccProfilingOn general flag was set (in
GHC.Driver.Ways.wayGeneralFlags
), and then this flag was queried in
various places.
There is no need to go via general flags, so this patch defines a
sccProfilingEnabled :: DynFlags -> Bool
helper function that just
checks whether WayProf is enabled.