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

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: na
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: na
  - task: lint_javascript_benchmarks
    status: na
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: na
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: passed
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: passed
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: kgryte

lib/node_modules/@stdlib/blas/ext/base/dfill/benchmark/c/benchmark.length.c

@@ -96,10 +96,11 @@ static double rand_double( void ) {
 */
 static double benchmark1( int iterations, int len ) {
 	double elapsed;
-	double x[ len ];
+	double *x;
 	double t;
 	int i;
 
+	x = (double *) malloc( len * sizeof( double ) );
 	for ( i = 0; i < len; i++ ) {
 		x[ i ] = ( rand_double()*200.0 ) - 100.0;
 	}
@@ -115,6 +116,7 @@ static double benchmark1( int iterations, int len ) {
 	if ( x[ 0 ] != x[ 0 ] ) {
 		printf( "should not return NaN\n" );
 	}
+	free( x );
 	return elapsed;
 }
 
@@ -127,10 +129,11 @@ static double benchmark1( int iterations, int len ) {
 */
 static double benchmark2( int iterations, int len ) {
 	double elapsed;
-	double x[ len ];
+	double *x;
 	double t;
 	int i;
 
+	x = (double *) malloc( len * sizeof( double ) );
 	for ( i = 0; i < len; i++ ) {
 		x[ i ] = ( rand_double()*200.0 ) - 100.0;
 	}
@@ -146,6 +149,7 @@ static double benchmark2( int iterations, int len ) {
 	if ( x[ 0 ] != x[ 0 ] ) {
 		printf( "should not return NaN\n" );
 	}
+	free( x );
 	return elapsed;
 }