libsparse: fix building on linux host.

memset is declared in <string.h>

Test: builds and works on host

Change-Id: I224a01c78ee1d0c2f8d5e86eef10c84c8960cbc0

libsparse/sparse_read.cpp

@@ -25,6 +25,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <string>
 #include <unistd.h>