Use SHA1 to verify libbcc is consistent with cache

Modify Android.mk to build a host version of sha1sum.
Modify bcc and MCCacheReader/Writer to check for sha1 on runtime.

Change-Id: I0aa32e2efd85e21f67cd46a20a9e55a430c41f30
diff --git a/lib/ExecutionEngine/Compiler.cpp b/lib/ExecutionEngine/Compiler.cpp
index 6f54dbc..4595d41 100644
--- a/lib/ExecutionEngine/Compiler.cpp
+++ b/lib/ExecutionEngine/Compiler.cpp
@@ -153,7 +153,7 @@
   if (GlobalInitialized)
     return;
 
-  LOGI("LIBBCC BUILD: %s\n", libbcc_build_time);
+  LOGI("LIBBCC BUILD CHECKSUM: %s\n", libbcc_build_checksum);
 
   // if (!llvm::llvm_is_multithreaded())
   //   llvm::llvm_start_multithreaded();