Nightly Dotty workflow of 2022-01-23 failed

[github-actions]

See https://github.com/lampepfl/dotty/actions/runs/1734802417

[michelou]

See line 485 in test-windows-full :

...
485 Fatal compiler crash when compiling: tests\run\forwardCompat-unusedImport: 
486 Cannot run program "C:\Windows\ServiceProfiles\NetworkService\.cache\dotty\test\compilers\scala3-3.0.2/bin/scalac": CreateProcess error=193, %1 is not a valid Win32 application 
487	at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048) 
488	at java.lang.Runtime.exec(Runtime.java:621) 
489	at java.lang.Runtime.exec(Runtime.java:486) 
490	at dotty.tools.vulpix.ParallelTesting$Test.compileWithOtherCompiler(ParallelTesting.scala:539) 
491	at dotty.tools.vulpix.ParallelTesting$CompilationLogic.compileTestSource$$anonfun$1$$anonfun$1(ParallelTesting.scala:222)
...

[som-snytt]

Duplicates #14300 where a PR is attached.