Redundant re-link when ".exe" omitted

[simonpj]

(Reported by Neil Mitchell.)

GHC 6.4.2 doesn't normally relink when invoked with --make if the target file has not changed. This is very very useful!

Create a Main.hs, and compile with ghc --make twice, first time it compiles, second time it does nothing.

Compile with ghc --make -o file.exe twice, first time it compiles, second time it does nothing.

Compile with ghc --make -o file (note the absence of .exe). First time it compiles as file.exe, second time and every time after it relinks. This is the bug. On Windows -o file means -o file.exe, and I guess the file "file" rather than "file.exe" is checked if it is up to date or not.

[simonmar]

Already fixed in HEAD, I don't think this one is critical enough to be worth fixing in 6.4.3.