xoptional.bool_operation test fails with XSIMD and OpenMP enabled

[nodatapoints]

When configured with -DXTENSOR_USE_{XSIMD,OPENMP}=1 -DBUILD_TESTS=1 the test fails with

/tmp/xtensor/test/test_xoptional.cpp:92:
TEST CASE:  xoptional.bool_operation

/tmp/xtensor/test/test_xoptional.cpp:98: ERROR: CHECK_EQ( res(0, 1).value(), true ) is NOT correct!
  values: CHECK_EQ( {?}, true )

May be related to #1802. Compiler info attached.
gcc-info.txt

[JohanMabille]

The issue is due to a container in the xtl which is not thread-safe, see xtensor-stack/xtl#240. This container is used for storing the boolean part of optional containers in xtensor.