bench: refactor to use dynamic memory allocation in blas/ext/base/dsum

[opbot-xd]

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Progresses #8643.

Description

What is the purpose of this pull request?

This pull request:

• Refactors the C benchmarks for @stdlib/blas/ext/base/dsum to use dynamic memory allocation instead of static memory allocation for large arrays.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: replace static memory allocation of large arrays in C benchmarks with dynamic memory allocation (tracking issue) #8643
• [BUG]: Segmentation fault when running C benchmarks #369

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

This PR replaces static array declarations (e.g., double x[ len ]) with dynamic memory allocation using malloc() and free() to prevent potential segmentation faults on systems with limited stack memory.

Changes made:

• Replaced double x[ len ]; with double *x;
• Added x = (double *)malloc( len * sizeof( double ) );
• Added NULL check for allocation failure
• Added free( x ); before returning

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

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@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/dsum	$\color{green}345/345$ $\color{green}+0.00%$	$\color{green}13/13$ $\color{green}+0.00%$	$\color{green}4/4$ $\color{green}+0.00%$	$\color{green}345/345$ $\color{green}+0.00%$

The above coverage report was generated for the changes in this PR.

[kgryte]

LGTM