Make size of hypervisor heap a build parameter.

Bug: 117270899
Change-Id: Ie9fd8db6a795f65637035773cfb43cbf1b89b6ec
diff --git a/src/main.c b/src/main.c
index 7c02e6d..e800a1a 100644
--- a/src/main.c
+++ b/src/main.c
@@ -31,7 +31,7 @@
 
 #include "vmapi/hf/call.h"
 
-char ptable_buf[PAGE_SIZE * 40];
+char ptable_buf[PAGE_SIZE * HEAP_PAGES];
 
 /**
  * Blocks the hypervisor.