BenchmarkResults "out_stream" field setup fails on Windows

[FObersteiner]

zBench/zbench.zig

Line 251 in f88d20b

out_stream: std.io.BufferedWriter(1024, @TypeOf(std.io.getStdOut().writer())) = .{ .unbuffered_writer = std.io.getStdOut().writer() },

On Windows 10 / Zig 0.11, the type of stdout writer cannot be determined at compile-time

C:\Users\user\scoop\apps\zig\current\lib\std\os\windows.zig:1892:28: error: unable to evaluate comptime expression
                break :blk asm volatile (
                           ^~~
C:\Users\user\scoop\apps\zig\current\lib\std\os\windows.zig:1907:15: note: called from here
    return teb().ProcessEnvironmentBlock;
           ~~~^~
C:\Users\user\scoop\apps\zig\current\lib\std\io.zig:36:30: note: called from here
        return os.windows.peb().ProcessParameters.hStdOutput;
               ~~~~~~~~~~~~~~^~
C:\Users\user\scoop\apps\zig\current\lib\std\io.zig:50:34: note: called from here
        .handle = getStdOutHandle(),
                  ~~~~~~~~~~~~~~~^~
zbench.zig:253:125: note: called from here
    out_stream: std.io.BufferedWriter(1024, @TypeOf(std.io.getStdOut().writer())) = .{ .unbuffered_writer = std.io.getStdOut().writer() },

[FObersteiner]

related: #40

related PR: #39