[BUILD] Improve how to handle yield() in ARM.

[santiagorr]

Changes

The yield instruction was introduced in ARM processors more recent than armel. So building in armel ends up in "Error: selected processor does not support `yield' in ARM mode". Also, the __yield() intrinsic instruction is not understood for armel by g++. So let's do nothing for armel.

This armel build CI job has the patch applied: https://salsa.debian.org/science-team/opentelemetry-cpp/-/jobs/6543996

Ref: https://developer.arm.com/documentation/ddi0406/b/Application-Level-Architecture/Application-Level-Programmers--Model/Exceptions--debug-events-and-checks/The-Yield-instruction?lang=en

Fixes #3128

P.S. Example of other project handling similar instructions in different architectures: https://github.com/geidav/spinlocks-bench/blob/master/os.hpp#L31

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: santiagorr / name: Santiago (c4ad65b)
• ✅ login: ThomsonTan / name: Tom Tan (05bc155)
• ✅ login: marcalff / name: Marc Alff (3b6d64a)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.85%. Comparing base (497eaf4) to head (3b6d64a).
Report is 157 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3129      +/-   ##
==========================================
+ Coverage   87.12%   87.85%   +0.73%     
==========================================
  Files         200      195       -5     
  Lines        6109     6138      +29     
==========================================
+ Hits         5322     5392      +70     
+ Misses        787      746      -41     

Files with missing lines	Coverage Δ
api/include/opentelemetry/common/spin_lock_mutex.h	25.00% <ø> (ø)

... and 100 files with indirect coverage changes

[lalitb]

LGTM if it is working fine with this patch for ARMel in the CI as mentioned in the description :)

[marcalff]

LGTM, based on the external armel build CI job provided.

Thanks for the fix.