Smaller and faster profile-build binaries

I have noticed that increasing the bench depth produces
progressively smaller and slightly faster executables at
the cost of longer compile times.  Also using bench "time"
instead of "depth" seems to produce slightly smaller/faster
executables  given comparable compile times.

I have made a new Makefile that generates smaller and
about 1% to 2% faster profile executables at only a
little extra compile time.  On  my mobile 2GHz i7 a
full profile build time goes from 3'48" to 4'13" and
the exe goes down by 5% from 416,310 bytes to 395,567
bytes.

No functional change.

src/Makefile

@@ -35,7 +35,7 @@ endif
 BINDIR = $(PREFIX)/bin
 
 ### Built-in benchmark for pgo-builds and signature
-PGOBENCH = ./$(EXE) bench 32 1 10 default depth
+PGOBENCH = ./$(EXE) bench 32 1 1 default time
 SIGNBENCH = ./$(EXE) bench
 
 ### Object files