-ddump-hi-diffs shouldn't imply -fforce-recomp, that defeats the purpose

compiler/main/DynFlags.hs

@@ -973,13 +973,13 @@ dynamic_flags = [
   ,  ( "dsource-stats",          setDumpFlag Opt_D_source_stats)
   ,  ( "dverbose-core2core",     setDumpFlag Opt_D_verbose_core2core)
   ,  ( "dverbose-stg2stg",       setDumpFlag Opt_D_verbose_stg2stg)
-  ,  ( "ddump-hi-diffs",         setDumpFlag Opt_D_dump_hi_diffs)
   ,  ( "ddump-hi",               setDumpFlag Opt_D_dump_hi)
   ,  ( "ddump-minimal-imports",  setDumpFlag Opt_D_dump_minimal_imports)
   ,  ( "ddump-vect",         	 setDumpFlag Opt_D_dump_vect)
   ,  ( "ddump-hpc",         	 setDumpFlag Opt_D_dump_hpc)
   ,  ( "ddump-mod-cycles",     	 setDumpFlag Opt_D_dump_mod_cycles)
   
+  ,  ( "ddump-hi-diffs",         NoArg (setDynFlag Opt_D_dump_hi_diffs))
   ,  ( "dcore-lint",       	 NoArg (setDynFlag Opt_DoCoreLinting))
   ,  ( "dstg-lint",        	 NoArg (setDynFlag Opt_DoStgLinting))
   ,  ( "dcmm-lint",		 NoArg (setDynFlag Opt_DoCmmLinting))