Build on MN5 with Intel compiler fails

[reuterbal]

What happened?

Building ifs-bundle with multio 2.10.1 fails on MN5 with several errors.

-- The C compiler identification is Intel 2021.10.0.20230609
-- The CXX compiler identification is Intel 2021.10.0.20230609

What are the steps to reproduce the bug?

ifs-bundle build of 49r3. Below log output is replicated for many files, only including the first two.

Version

2.10.1

Platform (OS and architecture)

Linux alogin1 5.14.0-284.30.1.el9_2.x86_64 #1 SMP PREEMPT_DYNAMIC Fri Aug 25 09:13:12 EDT 2023 x86_64 x86_64 x86_64 GNU/Linux

Relevant log output

In file included from /.../source/multio/src/multio/datamod/MarsMiscGeo.h(17),
                 from /.../source/multio/src/multio/mars2mars/rules/Matcher.h(13),
                 from /.../source/multio/src/multio/mars2mars/rules/Rule.h(13),
                 from /.../source/multio/src/multio/mars2mars/rules/Rule.cc(12):
/.../source/multio/src/multio/datamod/MarsKeys.h(51): error: expression must have a constant value
      EntryDef<std::string>{"stream"}
      ^
Note: cannot call non-constexpr function "std::optional<_Tp>::optional() noexcept [with _Tp=std::string_view]" (declared at line 694 of "/usr/include/c++/11/optional")

In file included from /.../source/multio/src/multio/action/scale/Scale.h(7),
                 from /.../source/multio/src/multio/action/scale/Scale.cc(11):
/.../source/multio/src/multio/datamod/MarsKeys.h(186): error: expression must have a constant value
      EntryDef<std::int64_t>{"frequency"}
      ^
Note: cannot call non-constexpr function "std::optional<_Tp>::optional() noexcept [with _Tp=std::string_view]" (declared at line 694 of "/usr/include/c++/11/optional")

Accompanying data

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Organisation

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