run-command: use ALLOC_ARRAY

Use the macro ALLOC_ARRAY to allocate an array.  This is shorter and
easier, as it automatically infers the size of elements.

Patch generated with Coccinelle and contrib/coccinelle/array.cocci.

Signeg-off-by: Rene Scharfe <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rscharfe

run-command.c

@@ -452,7 +452,7 @@ static char **prep_childenv(const char *const *deltaenv)
 	}
 
 	/* Create an array of 'char *' to be used as the childenv */
-	childenv = xmalloc((env.nr + 1) * sizeof(char *));
+	ALLOC_ARRAY(childenv, env.nr + 1);
 	for (i = 0; i < env.nr; i++)
 		childenv[i] = env.items[i].util;
 	childenv[env.nr] = NULL;