[C++] iso_calendar may be uninitialized

[asfimport]

/arrow/cpp/src/arrow/scalar.h:137:64: warning: ‘*((void*)& iso_calendar +8)’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  137 |       : PrimitiveScalarBase(std::move(type), true), value(value) {}
      |                                                                ^
In file included from /tmp/RtmpoS4YCn/file8773f4430f/src/arrow/CMakeFiles/arrow_objlib.dir/Unity/unity_17_cxx.cxx:7:
/arrow/cpp/src/arrow/compute/kernels/scalar_temporal.cc:697:30: note: ‘*((void*)& iso_calendar +8)’ was declared here
  697 |       std::array<int64_t, 3> iso_calendar;

fyi @rok

Reporter: Neal Richardson / @nealrichardson
Assignee: David Li / @lidavidm
Watchers: Rok Mihevc / @rok

Related issues:

• [C++] Fix use of non-const references in temporal kernels (is duplicated by)

PRs and other links:

• GitHub Pull Request #11121

_{Note: This issue was originally created as ARROW-13961. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
I just merged something here from @aucahuasi that may be relevant. (I could take care of this when I go back and fix ARROW-13960 as well since it's all around the same code.)

[asfimport]

Rok Mihevc / @rok:
  @nealrichardson  do you have a link to the run that produced this? The commit @lidavidm  is mentioned is a47b78a.

[asfimport]

Neal Richardson / @nealrichardson:
https://dev.azure.com/ursacomputing/crossbow/_build/results?buildId=11314&view=logs&j=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&t=6c939d89-0d1a-51f2-8b30-091a7a82e98c&l=461

[asfimport]

David Li / @lidavidm:
Issue resolved by pull request 11121
#11121