[Fuzzing X64] [Copilot] Fix Base64.DecodeFromUtf8 consuming whitespace in pa ...

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Job completed in 13 minutes 31 seconds (remote runner delay: 2 minutes 10 seconds).

Using arguments: fuzz Base64 -helix -NoPRLink
Main commit: dotnet/runtime@8fafcb3
PR commit: dotnet/runtime@49469ab

ERROR: System.Exception: prepare-fuzzer.bat  failed with exit code 1
   at Runner.JobBase.RunProcessAsync(String fileName, String arguments, List`1 output, String logPrefix, String workDir, Boolean checkExitCode, Func`2 processLogs, Boolean suppressOutputLogs, Boolean suppressStartingLog, ProcessPriorityClass priority, List`1 envVars, CancellationToken cancellationToken) in C:\h\w\A483088C\w\AAEF095F\e\runtime-utils\Runner\JobBase.cs:line 472
   at Runner.Jobs.FuzzLibrariesJob.BuildRuntimeAndPrepareFuzzerAsync() in C:\h\w\A483088C\w\AAEF095F\e\runtime-utils\Runner\Jobs\FuzzLibrariesJob.cs:line 77
   at Runner.Jobs.FuzzLibrariesJob.RunJobCoreAsync() in C:\h\w\A483088C\w\AAEF095F\e\runtime-utils\Runner\Jobs\FuzzLibrariesJob.cs:line 34
   at Runner.JobBase.RunJobAsync() in C:\h\w\A483088C\w\AAEF095F\e\runtime-utils\Runner\JobBase.cs:line 164

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