Don't have the string “debug.bcc.nocache” scattered in Script.cpp.

bccPrepareSharedObject() will also use isCacheable() function to set up the
cache.

Change-Id: I3d6a09348398beb0987bd747ad5ed13b6fb1ddb0
diff --git a/lib/ExecutionEngine/Script.h b/lib/ExecutionEngine/Script.h
index 5a42db6..8f78683 100644
--- a/lib/ExecutionEngine/Script.h
+++ b/lib/ExecutionEngine/Script.h
@@ -204,6 +204,7 @@
     char *getContext();
 #endif
 
+    bool isCacheable() const;
 
     void setError(int error) {
       if (mErrorCode == BCC_NO_ERROR && error != BCC_NO_ERROR) {