Fix Portable build

Forgot to add a new sourcefile to the makefile.

Change-Id: I79ae0f1742b1d1215c3f2940e4ca468d17a184ce
diff --git a/build/Android.libart-compiler-llvm.mk b/build/Android.libart-compiler-llvm.mk
index c072792..daef06e 100644
--- a/build/Android.libart-compiler-llvm.mk
+++ b/build/Android.libart-compiler-llvm.mk
@@ -40,6 +40,7 @@
 	src/compiler/dataflow.cc \
 	src/compiler/frontend.cc \
 	src/compiler/ralloc.cc \
+	src/compiler/bb_opt.cc \
 	src/compiler/ssa_transformation.cc \
 	src/compiler/compiler_utility.cc \
 	src/compiler/codegen/ralloc_util.cc \