add real mallinfo implementation for Android

Android Q uses the mallinfo implementation in the ART GC:

c220f98180
1575267302

test/Makefile

@@ -8,7 +8,8 @@ CPPFLAGS += \
     -DSLAB_CANARY=$(CONFIG_SLAB_CANARY)
 
 EXECUTABLES := \
-    offset
+    offset \
+    mallinfo
 
 all: $(EXECUTABLES)
 

test/mallinfo.c

@@ -0,0 +1,21 @@
+#include <malloc.h>
+
+__attribute__((optimize(0)))
+int main(void) {
+    malloc(1024 * 1024 * 1024);
+    malloc(16);
+    malloc(32);
+    malloc(64);
+
+    struct mallinfo info = mallinfo();
+    printf("arena: %zu\n", info.arena);
+    printf("ordblks: %zu\n", info.ordblks);
+    printf("smblks: %zu\n", info.smblks);
+    printf("hblks: %zu\n", info.hblks);
+    printf("hblkhd: %zu\n", info.hblkhd);
+    printf("usmblks: %zu\n", info.usmblks);
+    printf("fsmblks: %zu\n", info.fsmblks);
+    printf("uordblks: %zu\n", info.uordblks);
+    printf("fordblks: %zu\n", info.fordblks);
+    printf("keepcost: %zu\n", info.keepcost);
+}