[Fuzzing X64] [MihaZupan] Use local dotnet SDK for fuzzing code coverage

[MihuBot]

Job completed in 1 hour 38 minutes (remote runner delay: 1 minute 8 seconds).
dotnet/runtime#123597
Using arguments: fuzz Base64Fuzzer -helix
Main commit: dotnet/runtime@b19edc0
PR commit: MihaZupan/runtime@d55270b

Ran the fuzzer(s) successfully.

Code coverage reports:

• Base64Fuzzer

Artifacts:

• Base64Fuzzer-inputs.zip (1 MB)
• Base64Fuzzer-coverage.zip (394 KB)