[Bug 39244] scrrun:filesystem BOM tests fail in the Korean and Chinese locales

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=39244

Robert Wilhelm  changed:

What    |Removed                     |Added
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--- Comment #2 from Robert Wilhelm  ---
In dlls/scrrun/filesystem.c append_read_data() we check if last char in buf is
IsDBCSLeadByte and move it to next read.
But if last char in textstream is LeadByte, it will be ignored.

Tests behave different, we do not check for leadbyte here.

This leads to test failure because second bom byte (0xFE) is Leadbyte in e.g.
CN locale.