Handle both bugged and unbugged __sinit_ behaviors

[tclamb]

After making some progress in my decomp project, I found some of these symbols had different lengths of padding. After a bit of poking around in ghidra, I figured out what's actually going on.

The code that generates the static init symbol is similar to this line from the mac decomp:

sprintf(buf, "__sinit_%*.*s", -fname[0], fname[0], &fname[1]);

So fname is a length-prefixed dynamic string, right? But looking at mwccpsp.exe in Ghidra, its code is equivalent to something like:

sprintf(buf, "__sinit_%*.*s", -fname[0], fname[0], fname);

Lo and behold, debugging the process, I see that fname is indeed not length-prefixed. It's padding these symbols based on the first character of the filename.

This change updates mwccgap to work for non-bugged versions, and to reproduce the bug when present.