Add a note rather than repeating the full command

street/README.md

@@ -48,18 +48,14 @@ sudo pip install numpy
 
 Build the LSTM op:
 
-Linux
 ```
 cd cc
 TF_INC=$(python -c 'import tensorflow as tf; print(tf.sysconfig.get_include())')
 g++ -std=c++11 -shared rnn_ops.cc -o rnn_ops.so -fPIC -I $TF_INC -O3 -mavx
 ```
-Mac
-```
-cd cc
-TF_INC=$(python -c 'import tensorflow as tf; print(tf.sysconfig.get_include())')
-g++ -std=c++11 -shared rnn_ops.cc -o rnn_ops.so -fPIC -I $TF_INC -O3 -mavx -undefined dynamic_lookup
-```
+
+(Note: if running on Mac, add `-undefined dynamic_lookup` to the end of your
+`g++` command.)
 
 Run the unittests: