No more backtrace when using PHAR

[theredled]

Q	A
PHPUnit version	9.5.1
PHP version	7.4.13
Installation Method	PHAR

Summary

I don't have any backtrace anymore, all lines are filtered out in Filter::shouldPrintFrame.

It seems "logical" to me, as Filter::getFilteredStacktrace calls Filter::shouldPrintFrame with __PHPUNIT_PHAR_ROOT__ as a $prefix parameter.
But in Filter::shouldPrintFrame, a non-empty $prefix leads to an always-false return value at line 76 :

return $prefix === null && self::fileIsExcluded($file, $excludeList) && \is_file($file);

Therefore all lines are ignored.

Current behavior

I don't have any backtrace anymore, whatever error level it is.

How to reproduce

Produce an error or simply a failed assertion.

Expected behavior

Having a backtrace to debug the problem.

[sebastianbergmann]

Duplicate of #4573.