Had to also install libgmp-dev on Ubuntu 18.04.

tmciver · tmciver · commit d67ebf20aa6f · 2018-12-17T15:21:33.000-05:00
diff --git a/README.md b/README.md
@@ -101,7 +101,7 @@ not supported in master.
 On linux derivatives you will need to do the equivalent of before building
 
 ```bash
-sudo apt install libicu-dev libtinfo-dev
+sudo apt install libicu-dev libtinfo-dev libgmp-dev
 ```
 
 
