Parmap testsuite crash

[abbysmal]

Parmap seems to segfaults when running its testsuite against Multicore: Excerpt from: http://check.ocamllabs.io:8082/log/1624991904-364a3dc92d821c5de168ef561a9f2a79860cfafc/4.12+domains/bad/parmap.1.2.3

# Parmap warning: result order is not preserved (it was not expected to be).
# Speedup with 9 cores (average on 2 iterations): 3.157710 (tseq=3.333536, tpar=1.055682)
# Parmap warning: result order is not preserved (it was not expected to be).
# Parmap warning: result order is not preserved (it was not expected to be).
# Speedup with 10 cores (average on 2 iterations): 2.374792 (tseq=3.333536, tpar=1.403717)
# simplescale_array alias tests/runtest (got signal SEGV)
# (cd _build/default/tests && ./simplescale_array.exe)
# Testing scalability with 2 iterations on 1 to 10 cores, step 1
# Sequential execution takes 3.827161 seconds