RecEvent.TestMuonZipInfrastructure is failing for clang11-opt

The RecEvent.TestMuonZipInfrastructure test fails consistently only for clang11-opt. For some reason the condition of the test (that vector loops are faster than scalar loops) is violated for this platform. The last time the test was successful was with clang 8.

/cc @clemenci @chasse

Running 3 test cases...
Test timing of scalar and vectorised loops
Elapsed time (vector loops): 425 micro s. (Try 0)
Elapsed time (scalar loops): 327 micro s. (Try 0)
Failed
Elapsed time (vector loops): 480 micro s. (Try 1)
Elapsed time (scalar loops): 313 micro s. (Try 1)
Failed
Elapsed time (vector loops): 496 micro s. (Try 2)
Elapsed time (scalar loops): 354 micro s. (Try 2)
Failed
Elapsed time (vector loops): 439 micro s. (Try 3)
Elapsed time (scalar loops): 315 micro s. (Try 3)
Failed
Elapsed time (vector loops): 440 micro s. (Try 4)
Elapsed time (scalar loops): 330 micro s. (Try 4)
Failed
Elapsed time (vector loops): 471 micro s. (Try 5)
Elapsed time (scalar loops): 355 micro s. (Try 5)
Failed
Elapsed time (vector loops): 491 micro s. (Try 6)
Elapsed time (scalar loops): 368 micro s. (Try 6)
Failed
Elapsed time (vector loops): 474 micro s. (Try 7)
Elapsed time (scalar loops): 307 micro s. (Try 7)
Failed
Elapsed time (vector loops): 431 micro s. (Try 8)
Elapsed time (scalar loops): 315 micro s. (Try 8)
Failed
Elapsed time (vector loops): 439 micro s. (Try 9)
Elapsed time (scalar loops): 287 micro s. (Try 9)
Failed
Elapsed time (vector loops): 481 micro s. (Try 10)
Elapsed time (scalar loops): 283 micro s. (Try 10)
Failed
Elapsed time (vector loops): 442 micro s. (Try 11)
Elapsed time (scalar loops): 283 micro s. (Try 11)
Failed
Elapsed time (vector loops): 462 micro s. (Try 12)
Elapsed time (scalar loops): 343 micro s. (Try 12)
Failed
Elapsed time (vector loops): 468 micro s. (Try 13)
Elapsed time (scalar loops): 341 micro s. (Try 13)
Failed
Elapsed time (vector loops): 437 micro s. (Try 14)
Elapsed time (scalar loops): 300 micro s. (Try 14)
Failed
/workspace/build/LHCb/Event/RecEvent/tests/src/TestMuonZipInfrastructure.cpp(166): [1;31;49merror: in "test_timing_of_ismuon": check ( 2 * n_success > tries ) has failed[0;39;49m
Success 0 / 15

[1;31;49m*** 1 failure is detected in the test module "utestZipInfrastructure"
[0;39;49m