On Windows default to main.exe instead of a.out.
-- dependencies, and eliminating duplicates.
o_file <- readIORef v_Output_file
+#if defined(mingw32_HOST_OS)
+ let output_fn = case o_file of { Just s -> s; Nothing -> "main.exe"; }
+#else
let output_fn = case o_file of { Just s -> s; Nothing -> "a.out"; }
+#endif
pkg_lib_paths <- getPackageLibraryPath dep_packages
let pkg_lib_path_opts = map ("-L"++) pkg_lib_paths