Restore malloc debug.

Some libc changes were preventing the initialization call from being made.
The basic problem appears to be that libc_init_common.c is only built once,
and it's only built for the non-debug libc.
diff --git a/libc/bionic/libc_init_dynamic.c b/libc/bionic/libc_init_dynamic.c
index b8e1078..b479b27 100644
--- a/libc/bionic/libc_init_dynamic.c
+++ b/libc/bionic/libc_init_dynamic.c
@@ -77,6 +77,13 @@
     tls_area[TLS_SLOT_BIONIC_PREINIT] = NULL;
 
     __libc_init_common(elfdata);
+
+#ifdef MALLOC_LEAK_CHECK
+    /* setup malloc leak checker, requires system properties */
+    extern void malloc_debug_init(void);
+    malloc_debug_init();
+#endif
+
 }
 
 __noreturn void __libc_init(uintptr_t *elfdata,