Improve JIT time.

Change-Id: Iedeec580fb922b607f8cbc130dc952508a395408
diff --git a/bcc.cpp b/bcc.cpp
index 5fcb265..1f65625 100644
--- a/bcc.cpp
+++ b/bcc.cpp
@@ -261,7 +261,7 @@
      // -O1: llvm::CodeGenOpt::Less
      // -O2: llvm::CodeGenOpt::Default
      // -O3: llvm::CodeGenOpt::Aggressive
-    CodeGenOptLevel = llvm::CodeGenOpt::Aggressive;
+    CodeGenOptLevel = llvm::CodeGenOpt::None;
 
     // Below are the global settings to LLVM