[tlbuild] Intermittent W32TeX xdvipdfmx crashes

[Tim Eyre]

> Please try the latest TeX Live, if possible.

I've verified that the crash happens with the latest TeX Live 2020 binaries:

c:\work\xdvipdfmx_debug>cat test.bat
@echo off
xdvipdfmx --version | grep -m Version
xetex --version | grep -m W32TeX
xetex -no-pdf test.tex
:LOOPSTART
xdvipdfmx test.xdv
if "%ERRORLEVEL%"=="0" goto LOOPSTART
echo Failed with error %ERRORLEVEL%

c:\work\xdvipdfmx_debug>test.bat
This is xdvipdfmx Version 20210109 by the DVIPDFMx project team,
XeTeX 3.14159265-2.6-0.999992 (TeX Live 2020/W32TeX)
[...]
test.xdv -> test.pdf
[1][2][3][4][5][6][7][8]
11721 bytes written
test.xdv -> test.pdf
[1][2][3][4][5][6][7][8]Failed with error -1073741819

I am running Windows 10 version 20H2 build 19042.746, i7-8700 CPU,
36GB RAM. This crash is not causing a problem for me, so if you think
the issue is local to my system then we don't need to look at this any
further.

Tim