Add sequential `array_sum.c`

benchmarks/seq/array_sum.c

+#include <stdint.h> // uint8_t
+#include <stdlib.h> // EXIT_SUCCESS, size_t
+#include <string.h> // memcpy()
+
+#define T uint64_t
+#define X_LEN 10
+#define Y_LEN 10
+
+int main(void)
+{
+    T in[] = {
+        1,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,1,
+        2,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,2,
+        3,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,3,
+        4,0,0,0,0,0,0,0,
+        0,0,0,0,0,0,0,4
+    };
+    #define size (sizeof(in)/sizeof(T))
+    T out = 0;
+    for(size_t i = 0; i < size; i++) {
+        out += in[i];
+    }
+    return EXIT_SUCCESS;
+}