Symfony version(s) affected: 3.4

Description
When loading a class defined in eval()'d code DebugClassLoader::darwinRealpath() is unable to determine the real path of the file and a notice is triggered by the return $real .= $dirFiles[$kFile]; statement.

Additional context
The KernelTestCase PHPUnit 8 compatibility fix applied in #30124 defines KernelShutdownOnTearDownTrait in an eval() block and breaks the container compilation on mac.

[ErrorException]
Notice: Undefined index: kernelshutdownonteardowntrait.php(19) : eval()'d code 
Exception trace:
 () at /www/relendex/trading-api/vendor/symfony/debug/DebugClassLoader.php:450
 spl_autoload_call() at /www/relendex/trading-api/vendor/symfony/framework-bundle/Test/KernelTestCase.php:26

(The stack trace is from 4.2@dev, but the PR was merged to 3.4).