bench: refactor to use dynamic memory allocation in stats/strided/dmean

PR-URL: stdlib-js#9773
Ref: stdlib-js#8643

Reviewed-by: Philipp Burckhardt <pburckhardt@outlook.com>

Author: bhargava-d16

lib/node_modules/@stdlib/stats/strided/dmean/benchmark/c/benchmark.length.c

@@ -96,11 +96,11 @@ static double rand_double( void ) {
 */
 static double benchmark( int iterations, int len ) {
 	double elapsed;
-	double x[ len ];
+	double *x;
 	double v;
 	double t;
 	int i;
-
+	x = (double *) malloc( len * sizeof( double ) );
 	for ( i = 0; i < len; i++ ) {
 		x[ i ] = ( rand_double() * 20000.0 ) - 10000.0;
 	}
@@ -117,6 +117,7 @@ static double benchmark( int iterations, int len ) {
 	if ( v != v ) {
 		printf( "should not return NaN\n" );
 	}
+	free( x );
 	return elapsed;
 }